The Cyphernomicon

19. Appendices

19.1. copyright
THE CYPHERNOMICON: Cypherpunks FAQ and More, Version 0.666,
1994-09-10, Copyright Timothy C. May. All rights reserved.
See the detailed disclaimer. Use short sections under «fair
use» provisions, with appropriate credit, but don’t put your
name on my words.

19.2. SUMMARY: Appendices
19.2.1. Main Points
19.2.2. Connections to Other Sections
19.2.3. Where to Find Additional Information
19.2.4. Miscellaneous Comments

  • This is still under construction
  • Disorganized!!!
  • URLs need to be checked

19.3. Appendix — Sites, Addresses, URL/Web Sites, Etc.
19.3.1. be sure to get soda address straight!!! [use clones]

  • I received mine from soda.csua.berkeley.edu
    the menus are: /pub/cypherpunks/pgp/pgp26

19.3.2. How to use this section

  • comment on URLs being only a snapshot…
    • use reply to Sherry Mayo here
      19.3.3. General Crypto and Cypherpunks Sites
  • sci.crypt archive: anon ftp to ftp.wimsey.bc.ca:/pub/crypto
    [Mark Henderson]
  • ftp://soda.berkeley.edu/pub/cypherpunks/Home.html [has
    probably been changed to soda.csua.edu site]
    • ftp://ftp.u.washington.edu/public/phantom/cpunk/README.ht
      ml
  • ftp://furmint.nectar.cs.cmu.edu/security/cypheressay/what-
    is-cypherpunk.html [Vincent Cate, 1994-07-03]
  • ftp://wiretap.spies.com/Gov/World/usa.con
  • http://www.quadralay.com/www/Crypt/Crypt.html
  • http://cs.indiana.edu/ripem/dir.html
  • misc. article on crypto:
    http://www.quadralay.com/www/Crypt/Crypt.html
  • ftp.wimsey.bc.ca:/pub/crypto has REDOC III, Loki91, SHS and
    HAVAL (Mark Henderson, markh@vanbc.wimsey.com, 4-17-94,
    sci.crypt>
  • Some misc. ftp sites to check:
    • soda.berkeley.edu
    • ftp.informatik.uni-hamburg.de
    • ripem.msu.edu
    • garbo.uwasa.fi
    • wimsey.bc.ca
    • ghost.dsi.unimi.it
  • http://rsa.com
  • PC Expo disk package to ftp.wimsey.bc.ca [Arsen Ray
    Arachelian, 1994-07-05]
  • PC Expo disk
    • ftp.wimsey.bc.ca
      /pub/crypto/software/dist/US_or_Canada_only_XXXXXXXX/pcxp
      o/pcxpo.zip
  • «The FTP site ripem.msu.edu has a bunch of crypto stuff.»
    [Mark Riordan, 1994-07-08]
  • URL for «Applied Cryptography»-related files
  • http://www.mantis.co.uk/pgp/pgp.html
    • information on where to find PGP
  • pgpinfo@mantis.co.uk
    • send any mail to this site and receive a list back of PGP
      sites
  • PGP info: ftp.netcom.com, in /pub/gbe and in /pub/qwerty
  • more PGP:
    ftp:csn.org//mpj/I_will_not_export/crypto_???????/pgp
  • For non-U.S. sources of PGP: send blank mail to
    pgpinfo@mantis.co.uk
  • Sherry Mayo, a crypto researcher in Australia, is also
    making versions available:
    • «PGP2.6ui is available (I hope!) on my experimental WWW
      server, aim your browser at
      http://rschp2.anu.edu.au:8080/crypt.html I am new to
      this WWW thing so let me know if you have any probs
      downloading. Available on the server is:
      PGP2.6ui source for unix machines
      Executable for the PC version of PGP 2.6ui
      Executable for MacPGP 2.3″ [Sherry Mayo,
      talk.politics.crypto, 1994-09-06]
      19.3.5. Key Servers
  • pgp-public-keys@demon.co.uk
    • HELP in the subject line for more information about how
      to use
  • pgp-public-keys@jpunix.com
  • pgp-public-keys@pgp.iastate.edu
    • «help» as the subject, to get a list of keyservers
      [Michael Graff explorer@iastate.edu, alt.security.pgp,
      1994-07-04]
      19.3.6. Remailer Sites
  • To show active remailers: finger remailer@soda.berkeley.edu
    19.3.7. Mail-to-Usenet gateways:
  • group.name@paris.ics.uci.edu
    • group.name@cs.dal.ca
    • group.name@ug.cs.dal.ca

    • 19.3.8. Government Information
  • California Legislative Information
  • NSA Information
    • Can get on NSA/NCSC/NIST mailing list by sending to:
  • csrc.nist.gov:/pub/nistpubs
    19.3.9. Clipper Info
  • http://www.mantis.co.uk/~mathew/
    • some good Clipper articles and testimony
      19.3.10. Other
  • ftp://furmint.nectar.cs.cmu.edu/security/README.html#taxes
    • Vincent Cate
  • http://www.acns.nwu.edu/surfpunk/
  • Export Laws
    • «EFF Board member and Cygnus Support co-founder John
      Gilmore has set up a World Wide Web page on cryptography
      export issues, including information on how to apply for
      export clearance, exchages with Commerce Dept. on export
      licensing, legal documents on networking issues in
      relation to export of technology and crypto, and more.
      The URL is: http://www.cygnus.com/~gnu/export.html»
      [Stanton McCandlish, mech@eff.org, 1994-04-21]
  • Large integer math libraries
    • ripem.msu.edu
    • ftp:csn.org//mpj
  • Phrack
    • archived at ftp.netsys.com
  • Bruce Sterling’s comments at CFP
    • Bruce Sterling’s remarks delivered at the «Computers,
      Freedom and Privacy IV»
    • conference , Mar. 26 1994 in Chicago, are now online at
      EFF:
    • ftp://ftp.eff.org/pub/Publications/Bruce_Sterling/cfp_9
      4_sterling.speech
    • http://www.eff.org/pub/Publications/Bruce_Sterling/cfp_
      94_sterling.speech
    • gopher://gopher.eff.org/11/Publications/Bruce_Sterling/
      cfp_94_sterling.speech
    • gopher.eff.org, 1/Publications/Bruce_Sterling,
      cfp_94_sterling.speech
    • (source: Stanton McCandlish * mech@eff.org, 3-31-94)
      19.3.11. Crypto papers
  • ftp.cs.uow.edu.au
    pub/papers
  • (quantum, other, Siberry, etc.)
    19.3.12. CPSR URL
  • CPSR URL: http://www.cpsr.org/home

19.4. Appendix — Glossary
19.4.1. Comments

  • Release Note: I regret that I haven’t had time to add many
    new entries here. There are a lot of specialized terms, and
    I probably could have doubled the number of entries here.
  • Much more work is needed here. In fact, I debated at one
    point making the FAQ instead into a kind of «Encycopedia
    Cypherpunkia,» with a mix of short and long articles on
    each of hundreds of topics. Such an organization would
    suffer the disadvantages found in nearly all
    lexicographically-organized works: confusion of the
    concepts.
  • Many of the these entries were compiled for a long handout
    at the first Cypherpunks meeting, September, 1992. Errors
    are obviously present. I’ll try to keep correcting them
    when I can.
  • Schneier’s «Applied Cryptography» is of course an excellent
    place to browse for terms, special uses, etc.
    19.4.2. agoric systems — open, free market systems in which
    voluntary transactions are central.
    19.4.3. Alice and Bob — crypographic protocols are often made
    clearer by considering parties A and B, or Alice and Bob,
    performing some protocol. Eve the eavesdropper, Paul the
    prover, and Vic the verifier are other common stand-in names.
    19.4.4. ANDOS — all or nothing disclosure of secrets.
    19.4.5. anonymous credential — a credential which asserts some right
    or privelege or fact without revealing the identity of the
    holder. This is unlike CA driver’s licenses.
    19.4.6. assymmetric cipher — same as public key cryptosystem.
    19.4.7. authentication — the process of verifying an identity or
    credential, to ensure you are who you said you were.
    19.4.8. biometric security — a type of authentication using
    fingerprints, retinal scans, palm prints, or other
    physical/biological signatures of an individual.
    19.4.9. bit commitment — e.g., tossing a coin and then committing to
    the value without being able to change the outcome. The blob
    is a cryptographic primitive for this.
    19.4.10. BlackNet — an experimental scheme devised by T. May to
    underscore the nature of anonymous information markets. «Any
    and all» secrets can be offered for sale via anonymous
    mailers and message pools. The experiment was leaked via
    remailer to the Cypherpunks list (not by May) and thence to
    several dozen Usenet groups by Detweiler. The authorities are
    said to be investigating it.
    19.4.11. blinding, blinded signatures — A signature that the signer
    does not remember having made. A blind signature is always a
    cooperative protocol and the receiver of the signature
    provides the signer with the blinding information.
    19.4.12. blob — the crypto equivalent of a locked box. A
    cryptographic primitive for bit commitment, with the
    properties that a blobs can represent a 0 or a 1, that others
    cannot tell be looking whether it’s a 0 or a 1, that the
    creator of the blob can «open» the blob to reveal the
    contents, and that no blob can be both a 1 and a 0. An
    example of this is a flipped coin covered by a hand.
    19.4.13. BnD —
    19.4.14. Capstone —
    19.4.15. channel — the path over which messages are transmitted.
    Channels may be secure or insecure, and may have
    eavesdroppers (or enemies, or disrupters, etc.) who alter
    messages, insert and delete messages, etc. Cryptography is
    the means by which communications over insecure channels are
    protected.
    19.4.16. chosen plaintext attack — an attack where the cryptanalyst
    gets to choose the plaintext to be enciphered, e.g., when
    possession of an enciphering machine or algorithm is in the
    possession of the cryptanalyst.
    19.4.17. cipher — a secret form of writing, using substitution or
    transposition of characters or symbols. (From Arabic «sifr,»
    meaning «nothing.»)
    19.4.18. ciphertext — the plaintext after it has been encrypted.
    19.4.19. Clipper — the infamous Clipper chip
    19.4.20. code — a restricted cryptosystem where words or letters of a
    message are replaced by other words chosen from a codebook.
    Not part of modern cryptology, but still useful.
    19.4.21. coin flippping — an important crypto primitive, or protocol,
    in which the equivalent of flipping a fair coin is possible.
    Implemented with blobs.
    19.4.22. collusion — wherein several participants cooperate to deduce
    the identity of a sender or receiver, or to break a cipher.
    Most cryptosystems are sensitive to some forms of collusion.
    Much of the work on implementing DC Nets, for example,
    involves ensuring that colluders cannot isolate message
    senders and thereby trace origins and destinations of mail.
    19.4.23. COMINT —
    19.4.24. computationally secure — where a cipher cannot be broken
    with available computer resources, but in theory can be
    broken with enough computer resources. Contrast with
    unconditionally secure.
    19.4.25. countermeasure — something you do to thwart an attacker
    19.4.26. credential — facts or assertions about some entity. For
    example, credit ratings, passports, reputations, tax status,
    insurance records, etc. Under the current system, these
    credentials are increasingly being cross-linked. Blind
    signatures may be used to create anonymous credentials.
    19.4.27. credential clearinghouse — banks, credit agencies,
    insurance companies, police departments, etc., that correlate
    records and decide the status of records.
    19.4.28. cryptanalysis — methods for attacking and breaking ciphers
    and related cryptographic systems. Ciphers may be broken,
    traffic may be analyzed, and passwords may be cracked.
    Computers are of course essential.
    19.4.29. crypto anarchy — the economic and political system after the
    deployment of encryption, untraceable e-mail, digital
    pseudonyms, cryptographic voting, and digital cash. A pun on
    «crypto,» meaning «hidden,» and as when Gore Vidal called
    William F. Buckley a «crypto fascist.»
    19.4.30. cryptography — another name for cryptology.
    19.4.31. cryptology — the science and study of writing, sending,
    receiving, and deciphering secret messages. Includes
    authentication, digital signatures, the hiding of messages
    (steganography), cryptanalysis, and several other fields.
    19.4.32. cyberspace — the electronic domain, the Nets, and computer-
    generated spaces. Some say it is the «consensual reality»
    described in «Neuromancer.» Others say it is the phone
    system. Others have work to do.
    19.4.33. DC protocol, or DC-Net — the dining cryptographers protocol.
    DC-Nets use multiple participants communicating with the DC
    protocol.
    19.4.34. DES — the Data Encryption Standard, proposed in 1977 by the
    National Bureau of Standards (now NIST), with assistance from
    the National Security Agency. Based on the «Lucifer» cipher
    developed by Horst Feistel at IBM, DES is a secret key
    cryptosystem that cycles 64-bit blocks of data through
    multiple permutations with a 56-bit key controlling the
    routing. «Diffusion» and «confusion» are combined to form a
    cipher that has not yet been cryptanalyzed (see «DES,
    Security of»). DES is in use for interbank transfers, as a
    cipher inside of several RSA-based systems, and is available
    for PCs.
    19.4.35. DES, Security of — many have speculated that the NSA placed
    a trapdoor (or backdoor) in DES to allow it to read DES-
    encrypted messages. This has not been proved. It is known
    that the original Lucifer algorithm used a 128-bit key and
    that this key length was shortened to 64 bits (56 bits plus 8
    parity bits), ths making exhaustive search much easier (so
    far as is known, brute-force search has not been done, though
    it should be feasible today). Shamir and Bihan have used a
    technique called «differential cryptanalysis» to reduce the
    exhaustive search needed for chosen plaintext attacks (but
    with no import for ordinary DES).
    19.4.36. differential cryptanalysis — the Shamir-Biham technique for
    cryptanalyzing DES. With a chosen plaintext attack, they’ve
    reduced the number of DES keys that must be tried from about
    2^56 to about 2^47 or less. Note, however, that rarely can an
    attacker mount a chosen plaintext attack on DES systems.
    19.4.37. digital cash, digital money — Protocols for transferring
    value, monetary or otherwise, electronically. Digital cash
    usually refers to systems that are anonymous. Digital money
    systems can be used to implement any quantity that is
    conserved, such as points, mass, dollars, etc. There are
    many variations of digital money systems, ranging from VISA
    numbers to blinded signed digital coins. A topic too large
    for a single glossary entry.
    19.4.38. digital pseudonym — basically, a «crypto identity.» A way
    for individuals to set up accounts with various organizations
    without revealing more information than they wish. Users may
    have several digital pseudonyms, some used only once, some
    used over the course of many years. Ideally, the pseudonyms
    can be linked only at the will of the holder. In the simplest
    form, a public key can serve as a digital pseudonym and need
    not be linked to a physical identity.
    19.4.39. digital signature — Analogous to a written signature on a
    document. A modification to a message that only the signer
    can make but that everyone can recognize. Can be used
    legally to contract at a distance.
    19.4.40. digital timestamping — one function of a digital notary
    public, in which some message (a song, screenplay, lab
    notebook, contract, etc.) is stamped with a time that cannot
    (easily) be forged.
    19.4.41. dining cryptographers protocol (aka DC protocol, DC nets) —
    the untraceable message sending system invented by David
    Chaum. Named after the «dining philosophers» problem in
    computer science, participants form circuits and pass
    messages in such a way that the origin cannot be deduced,
    barring collusion. At the simplest level, two participants
    share a key between them. One of them sends some actual
    message by bitwise exclusive-ORing the message with the key,
    while the other one just sends the key itself. The actual
    message from this pair of participants is obtained by XORing
    the two outputs. However, since nobody but the pair knows the
    original key, the actual message cannot be traced to either
    one of the participants.
    19.4.42. discrete logarithm problem — given integers a, n, and x,
    find some integer m such that a^m mod n = x, if m exists.
    Modular exponentiation, the a^m mod n part, is
    straightforward (and special purpose chips are available),
    but the inverse problem is believed to be very hard, in
    general. Thus it is conjectured that modular exponentiation
    is a one-way function.
    19.4.43. DSS, Digital Signature Standard — the latest NIST (National
    Institute of Standards and Technology, successor to NBS)
    standard for digital signatures. Based on the El Gamal
    cipher, some consider it weak and poor substitute for RSA-
    based signature schemes.
    19.4.44. eavesdropping, or passive wiretapping — intercepting
    messages without detection. Radio waves may be intercepted,
    phone lines may be tapped, and computers may have RF
    emissions detected. Even fiber optic lines can be tapped.
    19.4.45. Escrowed Encryption Standard (EES) — current name for the
    key escrow system known variously as Clipper, Capstone,
    Skipjack, etc.
    19.4.46. factoring — Some large numbers are difficult to factor. It
    is conjectured that there are no feasible–i.e.»easy,» less
    than exponential in size of number– factoring methods. It is
    also an open problem whether RSA may be broken more easily
    than by factoring the modulus (e.g., the public key might
    reveal information which simplifies the problem).
    Interestingly, though factoring is believed to be «hard», it
    is not known to be in the class of NP-hard problems.
    Professor Janek invented a factoring device, but he is
    believed to be fictional.
    19.4.47. HUMINT —
    19.4.48. information-theoretic security — «unbreakable» security, in
    which no amount of cryptanalysis can break a cipher or
    system. One time pads are an example (providing the pads are
    not lost nor stolen nor used more than once, of course). Same
    as unconditionally secure.
    19.4.49. key — a piece of information needed to encipher or decipher
    a message. Keys may be stolen, bought, lost, etc., just as
    with physical keys.
    19.4.50. key exchange, or key distribution — the process of sharing a
    key with some other party, in the case of symmetric ciphers,
    or of distributing a public key in an asymmetric cipher. A
    major issue is that the keys be exchanged reliably and
    without compromise. Diffie and Hellman devised one such
    scheme, based on the discrete logarithm problem.
    19.4.51. known-plaintext attack — a cryptanalysis of a cipher where
    plaintext-ciphertext pairs are known. This attack searches
    for an unknown key. Contrast with the chosen plaintext
    attack, where the cryptanalyst can also choose the plaintext
    to be enciphered.
    19.4.52. listening posts — the NSA and other intelligence agencies
    maintain sites for the interception of radio, telephone, and
    satellite communications. And so on. Many sites have been
    identified (cf. Bamford), and many more sites are suspected.
    19.4.53. mail, untraceable — a system for sending and receiving mail
    without traceability or observability. Receiving mail
    anonymously can be done with broadcast of the mail in
    encrypted form. Only the intended recipient (whose identity,
    or true name, may be unknown to the sender) may able to
    decipher the message. Sending mail anonymously apparently
    requires mixes or use of the dining cryptographers (DC)
    protocol.
    19.4.54. Message Pool
    19.4.55. minimum disclosure proofs — another name for zero knowledge
    proofs, favored by Chaum.
    19.4.56. mixes — David Chaum’s term for a box which performs the
    function of mixing, or decorrelating, incoming and outgoing
    electronic mail messages. The box also strips off the outer
    envelope (i.e., decrypts with its private key) and remails
    the message to the address on the inner envelope. Tamper-
    resistant modules may be used to prevent cheating and forced
    disclosure of the mapping between incoming and outgoing mail.
    A sequence of many remailings effectively makes tracing
    sending and receiving impossible. Contrast this with the
    software version, the DC protocol. The «remailers» developed
    by Cypherpunks are an approximation of a Chaumian mix.
    19.4.57. modular exponentiation — raising an integer to the power of
    another integer, modulo some integer. For integers a, n, and
    m, a^m mod n. For example, 5^3 mod 100 = 25. Modular
    exponentiation can be done fairly quickly with a sequence of
    bit shifts and adds, and special purpose chips have been
    designed. See also discrete logarithm.
    19.4.58. National Security Agency (NSA) — the largest intelligence
    agency, responsible for making and breaking ciphers, for
    intercepting communications, and for ensuring the security of
    U.S. computers. Headquartered in Fort Meade, Maryland, with
    many listening posts around the world. The NSA funds
    cryptographic research and advises other agencies about
    cryptographic matters. The NSA once obviously had the world’s
    leading cryptologists, but this may no longer be the case.
    19.4.59. negative credential — a credential that you possess that you
    don’t want any one else to know, for example, a bankruptcy
    filing. A formal version of a negative reputation.
    19.4.60. NP-complete — a large class of difficult problems. «NP»
    stands for nondeterministic polynomial time, a class of
    problems thought in general not to have feasible algorithms
    for their solution. A problem is «complete» if any other
    NP problem may be reduced to that problem. Many important
    combinatorial and algebraic problems are NP-complete: the
    travelling salesman problem, the Hamiltonian cycle problem,
    the graph isomorphism problem, the word problem, and on and
    on.
    19.4.61. oblivious transfer — a cryptographic primitive that involves
    the probablistic transmission of bits. The sender does not
    know if the bits were received.
    19.4.62. one-time pad — a string of randomly-selected bits or symbols
    which is combined with a plaintext message to produce the
    ciphertext. This combination may be shifting letters some
    amount, bitwise exclusive-ORed, etc.). The recipient, who
    also has a copy of the one time pad, can easily recover the
    plaintext. Provided the pad is only used once and then
    destroyed, and is not available to an eavesdropper, the
    system is perfectly secure, i.e., it is information-
    theoretically secure. Key distribution (the pad) is
    obviously a practical concern, but consider CD-ROM’s.
    19.4.63. one-way function — a function which is easy to compute in
    one direction but hard to find any inverse for, e.g. modular
    exponentiation, where the inverse problem is known as the
    discrete logarithm problem. Compare the special case of trap
    door one-way functions. An example of a one-way operation
    is multiplication: it is easy to multiply two prime numbers
    of 100 digits to produce a 200-digit number, but hard to
    factor that 200-digit number.
    19.4.64. P ?=? NP — Certainly the most important unsolved problem
    in complexity theory. If P = NP, then cryptography as we know
    it today does not exist. If P = NP, all NP problems are
    «easy.»
    19.4.65. padding — sending extra messages to confuse eavesdroppers
    and to defeat traffic analysis. Also adding random bits to
    a message to be enciphered.
    19.4.66. PGP
    19.4.67. plaintext — also called cleartext, the text that is to be
    enciphered.
    19.4.68. Pool
    19.4.69. Pretty Good Privacy (PGP) — Phillip Zimmerman’s
    implementation of RSA, recently upgraded to version 2.0, with
    more robust components and several new features. RSA Data
    Security has threatened PZ so he no longer works on it.
    Version 2.0 was written by a consortium of non-U.S. hackers.
    19.4.70. prime numbers — integers with no factors other than
    themselves and 1. The number of primes is unbounded. About
    1% of the 100 decimal digit numbers are prime. Since there
    are about 10^70 particles in the universe, there are about
    10^23 100 digit primes for each and every particle in the
    universe!
    19.4.71. probabalistic encryption — a scheme by Goldwasser, Micali,
    and Blum that allows multiple ciphertexts for the same
    plaintext, i.e., any given plaintext may have many
    ciphertexts if the ciphering is repeated. This protects
    against certain types of known ciphertext attacks on RSA.
    19.4.72. proofs of identity — proving who you are, either your true
    name, or your digital identity. Generally, possession of the
    right key is sufficient proof (guard your key!). Some work
    has been done on «is-a-person» credentialling agencies, using
    the so-called Fiat-Shamir protocol…think of this as a way
    to issue unforgeable digital passports. Physical proof of
    identity may be done with biometric security methods. Zero
    knowledge proofs of identity reveal nothing beyond the fact
    that the identity is as claimed. This has obvious uses for
    computer access, passwords, etc.
    19.4.73. protocol — a formal procedure for solving some problem.
    Modern cryptology is mostly about the study of protocols for
    many problems, such as coin-flipping, bit commitment (blobs),
    zero knowledge proofs, dining cryptographers, and so on.
    19.4.74. public key — the key distributed publicly to potential
    message-senders. It may be published in a phonebook-like
    directory or otherwise sent. A major concern is the validity
    of this public key to guard against spoofing or
    impersonation.
    19.4.75. public key cryptosystem — the modern breakthrough in
    cryptology, designed by Diffie and Hellman, with
    contributions from several others. Uses trap door one-way
    functions so that encryption may be done by anyone with
    access to the «public key» but decryption may be done only by
    the holder of the «private key.» Encompasses public key
    encryption, digital signatures, digital cash, and many other
    protocols and applications.
    19.4.76. public key encryption — the use of modern cryptologic
    methods to provided message security and authentication. The
    RSA algorithm is the most widely used form of public key
    encryption, although other systems exist. A public key may be
    freely published, e.g., in phonebook-like directories, while
    the corresponding private key is closely guarded.
    19.4.77. public key patents — M.I.T. and Stanford, due to the work
    of Rivest, Shamir, Adleman, Diffie, Hellman, and Merkle,
    formed Public Key Partners to license the various public key,
    digital signature, and RSA patents. These patents, granted in
    the early 1980s, expire in the between 1998 and 2002. PKP has
    licensed RSA Data Security Inc., of Redwood City, CA, which
    handles the sales, etc.
    19.4.78. quantum cryptography — a system based on quantum-mechanical
    principles. Eavesdroppers alter the quantum state of the
    system and so are detected. Developed by Brassard and
    Bennett, only small laboratory demonstrations have been made.
    19.4.79. remailers — software versions of Chaum’s «mixes,» for the
    sending of untraceable mail. Various features are needed to
    do this: randomized order of resending, encryption at each
    stage (picked in advance by the sender, knowing the chain of
    remailers), padding of message sizes. The first remailer was
    written by E. Hughes in perl, and about a dozen or so are
    active now, with varying feature sets.
    19.4.80. reputations — the trail of positive and negative
    associations and judgments that some entity accrues. Credit
    ratings, academic credentials, and trustworthiness are all
    examples. A digital pseudonym will accrue these reputation
    credentials based on actions, opinions of others, etc. In
    crypto anarchy, reputations and agoric systems will be of
    paramount importance. There are many fascinating issues of
    how reputation-based systems work, how credentials can be
    bought and sold, and so forth.
    19.4.81. RSA — the main public key encryption algorithm, developed by
    Ron Rivest, Adi Shamir, and Kenneth Adleman. It exploits the
    difficulty of factoring large numbers to create a private key
    and public key. First invented in 1978, it remains the core
    of modern public key systems. It is usually much slower than
    DES, but special-purpose modular exponentiation chips will
    likely speed it up. A popular scheme for speed is to use RSA
    to transmit session keys and then a high-speed cipher like
    DES for the actual message text.
  • Description — Let p and q be large primes, typically with
    more than 100 digits. Let n = pq and find some e such that
    e is relatively prime to (p – 1)(q – 1). The set of numbers
    p, q, and e is the private key for RSA. The set of numbers
    n and e forms the public key (recall that knowing n is not
    sufficient to easily find p and q…the factoring problem).
    A message M is encrypted by computing M^e mod n. The owner
    of the private key can decrypt the encrypted message by
    exploiting number theory results, as follows. An integer d
    is computed such that ed =1 (mod (p – 1)(q – 1)). Euler
    proved a theorem that M^(ed) = M mod n and so M^(ed) mod n
    = M. This means that in some sense the integers e and d are
    «inverses» of each other. [If this is unclear, please see
    one of the many texts and articles on public key
    encryption.]
    19.4.82. secret key cryptosystem — A system which uses the same key
    to encrypt and decrypt traffic at each end of a communication
    link. Also called a symmetric or one-key system. Contrast
    with public key cryptosystem.
    19.4.83. SIGINT —
    19.4.84. smart cards — a computer chip embedded in credit card. They
    can hold cash, credentials, cryptographic keys, etc. Usually
    these are built with some degree of tamper-resistance. Smart
    cards may perform part of a crypto transaction, or all of it.
    Performing part of it may mean checking the computations of a
    more powerful computer, e.g., one in an ATM.
    19.4.85. spoofing, or masquerading — posing as another user. Used for
    stealing passwords, modifying files, and stealing cash.
    Digital signatures and other authentication methods are
    useful to prevent this. Public keys must be validated and
    protected to ensure that others don’t subsititute their own
    public keys which users may then unwittingly use.
    19.4.86. steganography — a part of cryptology dealing with hiding
    messages and obscuring who is sending and receiving messages.
    Message traffic is often padded to reduce the signals that
    would otherwise come from a sudden beginning of messages.
    «Covered writing.»
    19.4.87. symmetric cipher — same as private key cryptosystem.
    19.4.88. tamper-responding modules, tamper-resistant modules (TRMs) —
    sealed boxes or modules which are hard to open, requiring
    extensive probing and usually leaving ample evidence that the
    tampering has occurred. Various protective techniques are
    used, such as special metal or oxide layers on chips, armored
    coatings, embedded optical fibers, and other measures to
    thwart analysis. Popularly called «tamper-proof boxes.» Uses
    include: smart cards, nuclear weapon initiators,
    cryptographic key holders, ATMs, etc.
    19.4.89. tampering, or active wiretapping — intefering with messages
    and possibly modifying them. This may compromise data
    security, help to break ciphers, etc. See also spoofing.
    19.4.90. Tessera
    19.4.91. token — some representation, such as ID cards, subway
    tokens, money, etc., that indicates possession of some
    property or value.
    19.4.92. traffic analysis — determining who is sending or receiving
    messages by analyzing packets, frequency of packets, etc. A
    part of steganography. Usually handled with traffic padding.
    19.4.93. traffic analysis — identifying characteristics of a message
    (such as sender, or destination) by watching traffic.
    Remailers and encryption help to foil traffic analysys.
    19.4.94. transmission rules — the protocols for determining who can
    send messages in a DC protocol, and when. These rules are
    needed to prevent collision and deliberate jamming of the
    channels.
    19.4.95. trap messages — dummy messages in DC Nets which are used to
    catch jammers and disrupters. The messages contain no private
    information and are published in a blob beforehand so that
    the trap message can later be opened to reveal the disrupter.
    (There are many strategies to explore here.)
    19.4.96. trap-door — In cryptography, a piece of secret information
    that allows the holder of a private key to invert a normally
    hard to invert function.
    19.4.97. trap-door one way functions — functions which are easy to
    compute in both the forward and reverse direction but for
    which the disclosure of an algorithm to compute the function
    in the forward direction does not provide information on how
    to compute the function in the reverse direction. More simply
    put, trap-door one way functions are one way for all but the
    holder of the secret information. The RSA algorithm is the
    best-known example of such a function.
    19.4.98. unconditional security — same as information-theoretic
    security, that is, unbreakable except by loss or theft of the
    key.
    19.4.99. unconditionally secure — where no amount of intercepted
    ciphertext is enough to allow the cipher to be broken, as
    with the use of a one-time pad cipher. Contrast with
    computationally secure.
    19.4.100. URLs
    19.4.101. voting, cryptographic — Various schemes have been devised
    for anonymous, untraceable voting. Voting schemes should have
    several properties: privacy of the vote, security of the vote
    (no multiple votes), robustness against disruption by jammers
    or disrupters, verifiability (voter has confidence in the
    results), and efficiency.
    19.4.102. Whistleblowers
    19.4.103. zero knowledge proofs — proofs in which no knowledge of the
    actual proof is conveyed. Peggy the Prover demonstrates to
    Sid the Skeptic that she is indeed in possession of some
    piece of knowledge without actually revealing any of that
    knowledge. This is useful for access to computers, because
    eavesdroppers or dishonest sysops cannot steal the knowledge
    given. Also called minimum disclosure proofs. Useful for
    proving possession of some property, or credential, such as
    age or voting status, without revealing personal information.

19.5. Appendix — Summary of Crypto Versions
19.5.1. DOS and Windows

  • SecureDevice
  • SecureDrive
    • «Secdrv13d is the latest version. There was an unupdated
      .exe file in the package that had to be fixed. From the
      readme file: If you found this file inside FPART13D.ZIP,
      this is an update and bug fix for the FPART utility of
      SecureDrive Release 1.3d,
    • Edgar Swank involved?
  • SecureDevice
    • Major Versions:
    • Functions:
    • Principal Authors:
    • Major Platforms:
    • Where to Find:
    • ftp://ftp.csn.org/mpj/I_will_not_export/crypto_???????/
      secdrv/secdev.arj
      See ftp://ftp.csn.org/mpj/README.MPJ for the ???????
    • Strengths:
    • Weaknesses:
    • Notes:
    • By the way, I’m not the only one who gets SecureDrive
      and SecureDevice confused. Watch out for this.
  • SFS
    • «A MS-DOS-based package for hard disk encryption. It is
      implemented as a device driver and encrypts a whole
      partition (i.e., not a file or a directory). It uses the
      MDC/SHA cipher. … It is available from Grabo
      (garbo.uwasa.fi:/pc/crypt/sfs110.zip, I think), and also
      from our ftp site: ftp.informatik.uni-
      hamburg.de:/pub/virus/crypt/disk/sfs110.zip I would
      recommend the Garbo site, because ours is a bit slow.»
      [Vesselin Bontchev, alt.security.pgp, 1994-09-05]
    • Compared to SecureDrive, users report it to be faster,
      better-featured, has a Windows interface, is a device
      driver, and is robust. The disadvantages are that it
      currently does not ship with source code and uses a more
      obscure cipher.
    • «SFS (Secure FileSystem) is a set of programs which
      create and manage a number of encrypted disk volumes, and
      runs under both DOS and Windows. Each volume appears as
      a normal DOS drive, but all data stored on it is encryped
      at the individual-sector level….SFS 1.1 is a
      maintenance release which fixes a few minor problems in
      1.0, and adds a number of features suggested by users.
      More details on changes are given in in the README file.»
      [Peter Gutmann, sci.crypt, 1994-08-25]
    • «from garbo.uwasa.fi and all its mirror sites worldwide
      as /pc/crypt/sfs110.zip.»
  • WinCrypt.
    • «WinCrypt is pretty good IF you keep your encrypted text
      to less than the length of your password, AND IF you
      generate your password randomly, AND IF you only use each
      password ONCE. :-)» [Michael Paul Johnson, sci.crypt,
      1994-07-08]
  • Win PGP
    • there seem to be two identically-named programs:
    • WinPGP, by Christopher w. Geib
    • WinPGP, by Timothy M. Janke and Geoffrey C. Grabow
      • ftp WinPGP 1.0 from
        oak.oakland.edu//pub/msdos/windows3/WinPGP10.ZIP
    • Until this is clarified…
  • PGPShell
    • «PGPShell v3.2 has been released and is available at
      these sites: (U.S.)
      oak.oakland.edu:/pub/msdos/security/pgpshe32.zip
      (Euro)
      ftp.demon.co.uk:/simtel20/msdos/security/pgpshe32.zip
      [still@rintintin.Colorado.EDU (Johannes Kepler), 1994-07-
      07]
  • PGS
    • ftp.informatik.uni-
      hamburg.de:/pub/virus/crypt/pgp/shells/pgs099b.zip
    • «I just uploaded the bug fix of PGS (v0.99b) on some FTP-
      sites:
      wuarchive.wustl.edu:/pub/msdos_uploads/pgs/pgs099b.zip
      rzsun2.informatik.uni-hamburg.de:/pub/virus/crypt/pgp/…
      (Just uploaded it, should be on in a few days)
      oak.oakland.edu:/SimTel/msdos/security/pgs099b.zip (Just
      uploaded it, should be on in a few days) [Eelco Cramer crame001@hio.tem.nhl.nl, 1994-06-27]
  • DOS disk encryption utilities
    • Several free or nearly free utilities are available:
    • ftp.informatik.uni-hamburg.de:/pub/virus/crypt/disk/
      [Vesselin Vladimirov Bontchev, as of 1994-08]
    • Norton’s «Diskreet» is weak and essentially useless
    • uses DES in weak (ECB) mode…is probably the «snake
      oil» that Zimmermann writes about in his docs. SFS docs
      say it is even worse than that.
  • PGS
    • «PGS v0.99c is out there! This new version of PGS supports 8 bytes keyid’s.
      This version will be able to run in a OS/2 DOS box. PGS v0.99c is available on the following site:
      wuarchive.wustl.edu:/pub/msdos_uploads/pgs/pgs099c.zip»
      [ER CRAMER crame001@hio.tem.nhl.nl, 1994-07-08]
  • Program:
    • Major Versions:
    • Functions:
    • Principal Authors:
    • Major Platforms:
    • Where to Find:
    • Strengths:
    • Weaknesses:
    • Notes:
      19.5.2. OS/2
      19.5.3. Amiga
  • Program: PGPAmiga, Amiga PGP
    • Major Versions: 2.3a.4, PGP 2.6
    • «The Amiga equivalent of PGP 2.6ui is called PGP
      2.3a.3″ [unknown commenter]
    • Functions:
    • Principal Authors:
    • Major Platforms:
    • Where to Find:
    • Strengths:
    • Weaknesses:
    • Notes: Situation is confusing. 2.3a.3 is not equivalent
      to PGP 2.6ui.
      19.5.4. Unix
  • NeXTStep
  • Sun 4.3
  • Solaris
  • HP
  • SGI
  • swIPe
    • Metzger: It was John Ioannidis’ swIPe package, and it was
      not merely announced
      but released. Phil has done a similar package for KA9Q
      and was one of
      19.5.5. SFS ?
  • «A MS-DOS-based package for hard disk encryption. It is
    implemented as a device driver and encrypts a whole
    partition (i.e., not a file or a directory). It uses the
    MDC/SHA cipher. … It is available from Grabo
    (garbo.uwasa.fi:/pc/crypt/sfs110.zip, I think), and also
    from our ftp site: ftp.informatik.uni-
    hamburg.de:/pub/virus/crypt/disk/sfs110.zip I would
    recommend the Garbo site, because ours is a bit slow.»
    [Vesselin Bontchev, alt.security.pgp, 1994-09-05]
    19.5.6. Macintosh
  • more on MacPGPWell, I downloaded the rumoured MacPGP 2.6ui, but sadly
    it bombs out
    immediately with an address error when I try to run it. MacPGP 2.6ui works on my Quadra 605.
    The MacBinary process cannot handle pathnames >63
    characters, but as long
    an you encrypt files on the desktop, it’s not too much of
    a problem.
    • From: warlord@MIT.EDU (Derek Atkins)
      Newsgroups: alt.security.pgp
      Subject: Re: When will there be a bug fix for MacPGP?
      Followup-To: alt.security.pgp
      Date: 6 Jul 1994 10:19:13 GMT
      Organization: Massachusetts Institute of Technology
      Lines: 19
      Message-ID: WARLORD.94Jul6061917@toxicwaste.mit.edu
      References: AWILSON-020794082446@ts7-57.upenn.edu
      NNTP-Posting-Host: toxicwaste.media.mit.edu
      In-reply-to: AWILSON@DRUNIVAC.DREW.EDU’s message of 2 Jul
      1994 12:25:14 GMT In article AWILSON-020794082446@ts7-57.upenn.edu
      AWILSON@DRUNIVAC.DREW.EDU (AL WILSON) writes: When will there be a bug fix for MacPGP (1.1.1)? I am
      not complaining, I
      know that the software is free. I just want to start
      utilizing it for
      communications at the earliest possible time. There are still a number of outstanding bugs that need to
      be
      fixed, but the hope is to make a bugfix release in the
      near
      future. I don’t know when that is going to be, but
      hopefully
      it will be Real Soon Now (TM).
    • Date: Wed, 6 Jul 1994 10:42:08 -0700
      From: tcmay (Timothy C. May)
      To: tcmay
      Subject: (fwd) Re: What is the difference between 2.6 &
      2.6ui?
      Newsgroups: alt.security.pgp
      Organization: NETCOM On-line Communication Services (408
      261-4700 guest)
      Status: O Xref: netcom.com alt.security.pgp:16979
      Path: netcom.com!netcomsv!decwrl!lll-
      winken.llnl.gov!sol.ctr.columbia.edu!howland.reston.ans.n
      et!pipex!lyra.csx.cam.ac.uk!iwj10
      From: iwj10@cus.cam.ac.uk (Ian Jackson)
      Newsgroups: alt.security.pgp
      Subject: Re: What is the difference between 2.6 & 2.6ui?
      Date: Wed, 6 Jul 1994 10:14:24 GMT
      Organization: Linux Unlimited
      Lines: 55
      Message-ID:
      1994Jul6.101424.9203.chiark.ijackson@nyx.cs.du.edu
      References: CsE3CC.Gqz@crash.cts.com
      RATINOX.94Jul3221136@delphi.ccs.neu.edu
      NNTP-Posting-Host: bootes.cus.cam.ac.uk
      Summary: Use 2.6ui :-).
      Originator: iwj10@bootes.cus.cam.ac.uk —–BEGIN PGP SIGNED MESSAGE—– In article RATINOX.94Jul3221136@delphi.ccs.neu.edu,
      Stainless Steel Rat ratinox@ccs.neu.edu wrote:
    Ed Dantes edantes@crash.cts.com writes [quoting
    normalised – iwj]:subject line says it all.PGP 2.6 is distributed from MIT and is legally available
    to US and Canadian
    residents. It uses the RSAREF library. It has code that
    will prevent
    interoperation with earlier versions of PGP.PGP 2.6ui is a modified version of PGP 2.3a which
    functions almost
    identically to MIT PGP 2.6, without the «cripple code»
    of MIT PGP 2.6. It
    is legally available outside the US and Canada only. This is false. PGP 2.6ui is available to US and Canadian
    residents.
    It is definitely legal for such people to download PGP
    2.6ui and study
    it. However, RSADSI claim that using PGP 2.6ui in the US
    and Canada
    violates their patents on the RSA algorithm and on public
    key
    cryptography in general. Other people (like myself)
    believe that
    these patents wouldn’t stand up if tested in court, and
    that in any
    case the damages recoverable would be zero. You might also like to know that the output formats
    generated by 2.6ui
    and MIT-2.6 are identical, so that if you choose to use
    2.6ui in North
    America noone will be able to tell the difference anyway. Unfortunately these patent problems have caused many
    North American
    FTP sites to stop carrying 2.3a and 2.6ui, for fear of
    committing
    contributory infringement. If you would like to examine PGP 2.3a or 2.6ui, they are
    available on
    many FTP sites. Try
    black.ox.ac.uk:/src/security
    ftp.demon.co.uk:/pub/pgp
    ftp.dsi.unimi.it:/pub/security/crypt/PGP
    ftp.funet.fi:/pub/crypt
    for starters. Look out for the regular postings here in
    alt.security.pgp for other sites. —–BEGIN PGP SIGNATURE—–
    Version: 2.6 iQCVAgUBLhqD48MWjroj9a3bAQH9VgQAqOvCVXqJLhnFvsKfr82M5808h
    6GKY5RW
    SZ1/YLmshlDEMgeab4pSLSz+lDvsox2KFxQkP7O3oWYnswXcdr4FdLBu/
    TXU+IQw
    E4r/jY/IXSupP97Lxj9BB73TkJIHVmrqgoPQG2Nszj60cbE/LsiGs5uMn
    CSESypH
    c0Y8FnR64gc=
    =Pejo
    —–END PGP SIGNATURE—–
    —
    Ian Jackson, at home ijackson@nyx.cs.du.edu or
    iwj10@cus.cam.ac.uk
    +44 223 575512 Escoerea on IRC.
    http://www.cl.cam.ac.uk/users/iwj10/
    2 Lexington Close, Cambridge, CB4 3LS, England. Urgent:
    iwj@cam-orl.co.uk —
    …………………………………………………
    ……………..
    Timothy C. May | Crypto Anarchy: encryption,
    digital money,
    tcmay@netcom.com | anonymous networks, digital
    pseudonyms, zero
    408-688-5409 | knowledge, reputations,
    information markets,
    W.A.S.T.E.: Aptos, CA | black markets, collapse of
    governments.
    Higher Power: 2^859433 | Public Key: PGP and MailSafe
    available.
    «National borders are just speed bumps on the information
    superhighway.»
  • CurveEncrypt, for Mac
    • «Curve Encrypt 1.1, IDEA encryption for the Macintosh is
      now available…..Curve Encrypt is a freeware drag-and-
      drop encryption application for the Macintosh. It uses
      IDEA cipher-feedback mode with a 255 character pass
      phrase, encrypts both the data and resource forks of
      files, and will encrypt the contents of a folder or
      volume in a single operation. Source code is provided,
      natch. CE is System 7 only….(Note that this program has
      nothing whatsoever to do with elliptic curve
      encryption methods, just so nobody gets confused…)» [
      «W. Kinney» kinney@bogart.Colorado.EDU, 1994-07-08]
    • «Ftp Sites: ripem.msu.edu:pub/crypt/other/curve-encrypt-idea-for-mac/
      This is an export controlled ftp site: read
      pub/crypt/GETTING_ACCESS for
      information. ftp.csn.org:/mpj/I_will_not_export/crypto_???????/curve_e
      ncrypt/
      csn.org is also export-controlled: read /mpj/README for
      the characters
      to replace ???????.» [ «W. Kinney»
      kinney@bogart.Colorado.EDU, 1994-07-08]
  • RIPEM on Macintosh
    • Carl Ellison says «I’ve only used RIPEM on AOL — but it
      should be the same….I run on a Mac, generating the
      armored file, and then use AOL’s «paste from file» option
      in the File menu to include the encrypted file in the
      body of my message…..In the other direction, I have to
      use Select All and Copy to get it out of AOL mail, Paste
      to get it into an editor. From there I can file it and
      give that file to PGP or RIPEM…..BBEDIT on the Mac has
      good support for RIPEM. I wish I knew how to write
      BBEDIT extensions for Mac PGP as well.» [C.E., 1994-07-
      06]
  • URL for Stego (Macintosh)
  • Several exist.
    • XSPLIT
    • cryptosplit, Ray Cromwell
    • shade

19.6. Appendix — References
19.6.1. the importance of libraries

  • «Use a library. That’s a place with lots of paper
    periodicals and paper books. Library materials not online,
    mostly, but it is still where most of the world’s encoded
    knowledge is stored. If you don’t like paper, tough.
    That’s the way the world is right now.» [Eric Hughes, 1994-
    04-07]
    19.6.2. Books
  • Bamford, James, «The Puzzle Palace,» 1982. The seminal
    reference on the NSA.
  • N. Koblitz, «A course in number theory and cryptography»,
    QA3.G7NO.114. Very technical, with an emphasis on elliptic
    functions.
  • D. Welsh, «Codes and Cryptography», Oxford Science Publications, 1988, Eric Hughes especially recommends this.
    • Z103.W461988
  • D.E. Denning, «Cryptography and Data Security», 1982,
    Addison-Wesley, 1982, QA76.9.A25D46. A classic, if a bit
    dated, introduction by the woman who later became the chief
    supporter of Clipper.
  • G. Brassard, «Modern Cryptology: a tutorial», Lecture Notes in Computer
    • Science 325, Springer 1988, QA76.L4V.325 A slim little
      book that’s a gem. Sections by David Chaum.
  • Vinge, V., «True Names,» 1981. A novel about digital
    pseudonyms and cyberspace.
  • Card, Orson Scott, «Ender’s Game,» 1985-6. Novel about kids
    who adopt digital pseudonyms for political debate.
  • G.J. Simmons,»Contemporary Cryptology», IEEE Press, 1992,
    QA76.9.A25C6678. A collection of articles by well-known
    experts. Surprisingly, no discussion of digital money. Gus
    Simmons designed «Permissive Action Links» for nukes, at
    Sandia.
    19.6.3. sci.crypt
  • archived at ripem.msu.edu and rpub.cl.msu.edu
    –
  • The cryptography anon ftp archive at wimsey.bc.ca:/pub/crypto
    • has been moved to ftp.wimsey.bc.ca
      19.6.4. cryptography-faq
  • in about 10 parts, put out by Crypt Cabal (several
    Cypherpunks on it)
  • rtfm.mit.edu, in /pub/usenet/news.answers/cryptography-
    faq/part[xx]
  • posted every 21 days to sci.crypt, talk.politics.crypto,
    • sci.answers, news.answers
      19.6.5. RSA FAQ
  • Paul Fahn, RSA Laboratories
  • anonymous FTP to rsa.com:/pub/faq
  • rtfm.mit.edu, /pub/usenet/news.answers/cryptography-faq/rsa
    19.6.6. Computers, Freedom and Privacy Conference
  • next Computers, Freedom and Privacy Conference will be
    March 1995, San Francisco
    19.6.7. Various computer security papers, publications, and programs
    can be found at cert.org.
  • anonymous ftp to it and look in /pub. /pub/info even has
    the NSA «Orange Book.» (Not a secret, obviously. Anyone can
    get on the NSA/NCSC’s mailing list and get a huge pile of
    documents sent to them, with new ones arriving every
    several weeks.)
  • or try ftp.win.tue.nl /pub/security
    19.6.8. Clipper information by Internet
  • ftp.cpsr.org
  • ftp.eff.org

19.7. Glossary Items
19.7.1. message pools —
19.7.2. pools — see «message pools.»
19.7.3. cover traffic —
19.7.4. padding — see «message padding.»
19.7.5. message padding —
19.7.6. latency —
19.7.7. BlackNet — an experiment in information markets, using
anonymous message pools for exchange of instructions and
items. Tim May’s experiment in guerilla ontology.
19.7.8. ILF — Information Liberation Front. Distributes copyrighted
material via remailers, anonymously. Another experiment in
guerilla ontology.
19.7.9. digital mix —
19.7.10. FinCEN — Financial Crimes Enforcement Network.
19.7.11. true name — one’s actual, physical name. Taken from Vernor
Vinge’s novel of the same name.
19.7.12. mix —
19.7.13. TEMPEST —
19.7.14. OTP —
19.7.15. Vernam cipher —
19.7.16. detweiler — verb, to rant and rave about tentacles that are
destroying one’s sanity through crypto anarchist thought
control. Named after L. Detweiler. «He’s just detweilering.»
19.7.17. remailer —
19.7.18. Stego —
19.7.19. incipits — message indicators or tags (relates to stego)
19.7.20. duress code — a second key which can decrypt a message to
something harmless. Could be useful for bank cards, as well
as for avoiding incrimination. A form of security through
obscurity, and not widely used.

19.8. A comment on software versions, ftp sites, instructions, etc.
19.8.1. I regret that I can’t be complete in all versions, platforms
supported, sites for obtaining, instructions,
incompatibilities, etc. Frankly, I’m drowning in reports of
new versions, questions about use, etc. Most of these
versions I have no direct knowledge of, have no experience
with, and no appreciation of subtle incompatibilites
involved.
19.8.2. There are others who have concentrated on providing up-to-
date reports on what is available. Some of them are»

  • site
    19.8.3. Reading sci.crypt, alt.security.pgp, and related groups for a
    few weeks and looking for programs of interest to one’s own
    situation should give the most recent and current results.
    Things are moving quickly, so if one is interested in
    «AmigaPGP,» for example, then the right place to look for the
    latest versions is in the groups just mentioned, or in groups
    and ftp sites specific to the Amiga. (Be careful that
    sabotaged or spoofed versions are not used, as in all crypto.
    «Joe’s AmigaPGP» might need a closer look.)

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