Cryptography for Smalltalkers - ESUG 2004
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ESUG 2004
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Cryptography for Smalltalkers - ESUG 2004
- 1. Cryptography for Smalltalkers Martin Kobetic Cincom Smalltalk Development ESUG 2004
Editor's Notes
- confidentiality - prevent eavesdropping (passive attack) integrity - prevent undetected modification (active attack) authentication - proof of origin (active attack) non-repudiation - undeniable proof of origin SSL provides authentication but doesn’t provide non-repudiation SMIME does both (theoretically) point-to-point vs end-to-end
- Hardware implementations
- Key stream reuse disastrous (P1 xor K) xor (P2 xor K) = P1 xor (K xor K) xor P2 = P1 xor P2 xoring 2 ciphertexts yields 2 xored plaintexts, easy to break
- ARC4 – “Alleged” RC4
- DEA (ANSI), DEA-1 (ISO) Lucifer descendant (IBM), NSA evaluated reviewed every 5 years 1983 – recertified, 1987 – recertified “last time” after public outcry 1993 – recertified, still no alternatives 1999 – reaffirmed 3DES, AES not finished yet
- POSITIVES parallelizable NEGATIVES preserves plaintext patterns easily manipulated
- N-bit OFB: smaller than block processing No need to pad. Doesn’t need decryption operation.
- Nonce: usually message number combined with additional data to guarantee uniqueness N-bit CTR: smaller than block processing No need to pad. Doesn’t need decryption operation.
- N-bit CFB: smaller than block processing No need to pad. Doesn’t need decryption operation.
- double encryption – meet in the middle attach 2^n+1 instead of 2^2n triple encryption – 2key or 3key cascading – beware of algorithm interactions
- Finalists Rijndael – Joan Daemen, Vincent Rijmen (Netherlands) Serpent – Ross Anderson (Cambridge, UK) Twofish – Bruce Schneier (Counterpane Inc) MARS – Don Coppersmith (IBM) RC6 – Ron Rivest (RSA Labs)