HASH ALGORITHMS MD 5 SHA RIPEMD160 HMAC MD

HASH ALGORITHMS • MD 5 • SHA • RIPEMD-160 • HMAC

MD 5 • Message Digest • Compression • Elementary Operations

MESSAGE DIGEST GENERATION MD 5

MD 5 COMPRESSION FUNCTION

ELEMENTARY MD 5 OPERATION

KEY ELEMENTS OF MD 5 • Table 9. 1 – truth table B C D || F G H I -------------------0 0 0 || 0 0 0 1 || 1 0 0 1 0 || 0 1 1 0 0 1 1 || 1 0 0 1 1 0 0 || 0 0 1 1 1 0 1 || 0 1 1 1 0 || 1 1 0 0 1 1 1 || 1 1 1 0

SECURE HASH ALGORITHM SHA-1 • Message Digest • Compression • Elementary Operations

SHA-1 COMPRESSION FUNCTION

ELEMENTARY SHA OPERATION

TRUTH TABLE for ft – SHA-1 B C D || f f 0. . 19 20. . 39 40. . 59 60. . 79 --------------------------------------0 0 1 1 0 1 0 1 | | | | 0 1 0 0 1 1 0 1 0 0 0 1 1 1 0 1 0 0 1

CREATION OF 80 -WORD I/P

Comparison: MD 5 vs SHA 1 MD 5 message digest – 128 bits SHA-1 message digest – 160 bits Find two messages with same digest: 64 MD 5 – 2 operations 80 SHA-1 - 2 operations

NEW SHA ALGORITHMS • SHA-256 • SHA-384 • SHA-512 message digest lengths: 256, 384, 512 to provide compatibility with AES (see Tables 12. 3 and 12. 4)

RIPEMD - 160 • Message Digest • Compression • Elementary Operations

RIPEMD – 160 COMPRESSION FUNCTION

RIPEMD – 160 ELEMENTARY OPERATION

RIPEMD – 160 - data Tables 12. 5 – 12. 9

HASH FUNCTIONS - comparisons Table 12. 8 - comparison Table 12. 9 - relative performance

HMAC – a MAC from a HASH Why? Hash functions (e. g. MD 5, SHA-1) execute faster than Sym. Key (e. g. DES) HMAC combines HASH with Secret Key to make a MAC HMACK(M) = H[(K+ + opad)||H[K+ + ipad)||M]] Security(H) Security(HMAC)

HMAC STRUCTURE

EFFICIENT IMPLEMENTATION of HMAC