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Cryptography FAQ (01/10: Overview)

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Archive-name: cryptography-faq/part01
Last-modified: 1999/06/27

See reader questions & answers on this topic! - Help others by sharing your knowledge
This is the first of ten parts of the sci.crypt FAQ. The parts are
mostly independent, but you should read this part before the rest. We
don't have the time to send out missing parts by mail, so don't ask.
Notes such as ``[KAH67]'' refer to the reference list in the last part.

Disclaimer: This document is the product of the Crypt Cabal, a secret
society which serves the National Secu---uh, no. Seriously, we're the
good guys, and we've done what we can to ensure the completeness and
accuracy of this document, but in a field of military and commercial
importance like cryptography you have to expect that some people and
organizations consider their interests more important than open
scientific discussion. Trust only what you can verify firsthand.
And don't sue us.

Many people have contributed to this FAQ. In alphabetical order:
Eric Bach, Steve Bellovin, Dan Bernstein, Nelson Bolyard, Carl Ellison,
Jim Gillogly, Mike Gleason, Doug Gwyn, Luke O'Connor, Tony Patti,
William Setzer. We apologize for any omissions.

Archives: sci.crypt has been archived since October 1991 on, though these archives are available only to U.S. and
Canadian users. Another site is in /pub/crypt/sci.crypt/ 
from Jan 1992.

The sections of this FAQ are available via anonymous FTP to 
as /pub/usenet/news.answers/cryptography-faq/part[xx]. The Cryptography 
FAQ is posted to the newsgroups sci.crypt, talk.politics.crypto, 
sci.answers, and news.answers every 21 days.

The fields `Last-modified' and `Version' at the top of each part track

1999: There is a project underway to reorganize, expand, and update the
sci.crypt FAQ, pending the resolution of some minor legal issues. The
new FAQ will have two pieces. The first piece will be a series of web
pages. The second piece will be a short posting, focusing on the
questions that really are frequently asked.

In the meantime, if you need to know something that isn't covered in the
current FAQ, you can probably find it starting from Ron Rivest's links
at <>.

If you have comments on the current FAQ, please post them to sci.crypt
under the subject line Crypt FAQ Comments. (The crypt-comments email
address is out of date.)

Table of Contents

1. Overview

2. Net Etiquette
2.1. What groups are around? What's a FAQ? Who am I? Why am I here?
2.2. Do political discussions belong in sci.crypt?
2.3. How do I present a new encryption scheme in sci.crypt?

3. Basic Cryptology
3.1. What is cryptology? Cryptography? Plaintext? Ciphertext? Encryption? Key?
3.2. What references can I start with to learn cryptology?
3.3. How does one go about cryptanalysis?
3.4. What is a brute-force search and what is its cryptographic relevance?
3.5. What are some properties satisfied by every strong cryptosystem?
3.6. If a cryptosystem is theoretically unbreakable, then is it
  guaranteed analysis-proof in practice?
3.7. Why are many people still using cryptosystems that are
  relatively easy to break?
3.8. What are the basic types of cryptanalytic `attacks'?

4. Mathematical Cryptology
4.1. In mathematical terms, what is a private-key cryptosystem?
4.2. What is an attack?
4.3. What's the advantage of formulating all this mathematically?
4.4. Why is the one-time pad secure?
4.5. What's a ciphertext-only attack?
4.6. What's a known-plaintext attack?
4.7. What's a chosen-plaintext attack?
4.8. In mathematical terms, what can you say about brute-force attacks?
4.9. What's a key-guessing attack? What's entropy?

5. Product Ciphers
5.1. What is a product cipher?
5.2. What makes a product cipher secure?
5.3. What are some group-theoretic properties of product ciphers?
5.4. What can be proven about the security of a product cipher?
5.5. How are block ciphers used to encrypt data longer than the block size?
5.6. Can symmetric block ciphers be used for message authentication?
5.7. What exactly is DES?
5.8. What is triple DES?
5.9. What is differential cryptanalysis?
5.10. How was NSA involved in the design of DES?
5.11. Is DES available in software?
5.12. Is DES available in hardware?
5.13. Can DES be used to protect classified information?
5.14. What are ECB, CBC, CFB, and OFB encryption?

6. Public-Key Cryptography
6.1. What is public-key cryptography?
6.2. How does public-key cryptography solve cryptography's Catch-22?
6.3. What is the role of the `trapdoor function' in public key schemes?
6.4. What is the role of the `session key' in public key schemes?
6.5. What's RSA?
6.6. Is RSA secure?
6.7. What's the difference between the RSA and Diffie-Hellman schemes?
6.8. What is `authentication' and the `key distribution problem'?
6.9. How fast can people factor numbers?
6.10. What about other public-key cryptosystems?
6.11. What is the `RSA Factoring Challenge?'

7. Digital Signatures
7.1. What is a one-way hash function?
7.2. What is the difference between public, private, secret, shared, etc.?
7.3. What are MD4 and MD5?
7.4. What is Snefru?

8. Technical Miscellany
8.1. How do I recover from lost passwords in WordPerfect?
8.2. How do I break a Vigenere (repeated-key) cipher?
8.3. How do I send encrypted mail under UNIX? [PGP, RIPEM, PEM, ...]
8.4. Is the UNIX crypt command secure?
8.5. How do I use compression with encryption?
8.6. Is there an unbreakable cipher?
8.7. What does ``random'' mean in cryptography?
8.8. What is the unicity point (a.k.a. unicity distance)?
8.9. What is key management and why is it important?
8.10. Can I use pseudo-random or chaotic numbers as a key stream?
8.11. What is the correct frequency list for English letters?
8.12. What is the Enigma?
8.13. How do I shuffle cards?
8.14. Can I foil S/W pirates by encrypting my CD-ROM?
8.15. Can you do automatic cryptanalysis of simple ciphers?
8.16. What is the coding system used by VCR+?

9. Other Miscellany
9.1. What is the National Security Agency (NSA)?
9.2. What are the US export regulations?
9.3. What is TEMPEST?
9.4. What are the Beale Ciphers, and are they a hoax?
9.5. What is the American Cryptogram Association, and how do I get in touch?
9.6. Is RSA patented?
9.7. What about the Voynich manuscript?

10. References
10.1. Books on history and classical methods
10.2. Books on modern methods
10.3. Survey articles
10.4. Reference articles
10.5. Journals, conference proceedings
10.6. Other
10.7. How may one obtain copies of FIPS and ANSI standards cited herein?
10.8. Electronic sources
10.9. RFCs (available from [FTPRF])
10.10. Related newsgroups

User Contributions:

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