From The ECRYPT Hash Function Website
Revision as of 11:41, 12 October 2006 by Nobbi (talk | contribs) (Message Expansion)

1 General Description

SHA-1 is an iterated hash function. It can be used to compute a 160-bit hash value for messages having a length of less than math bits, cf. FIPS 180-2 Secure Hash Standard. As most iterated hash functions, SHA-1 applies MD strengthening.

1.1 Compression Function

The compression function processes input message blocks of 512 bits and produces a 160-bit chaining value. The compression function of SHA-1 basically consists of two parts: the message expansion and the state update transformation. The chaining variable math (iv in the first iteration) is added to the output of the state update transformation (feed forward).

The SHA-1 compression function

1.1.1 Message Expansion

In SHA-1, the message expansion is defined as follows. A single 512-bit input message block block is represented by 16 32-bit words, denoted by math, with math. The message input is linearly expanded into 80 32-bit words math defined as follows:


1.1.2 State Update Transformation


1.2 Padding Method

1.3 Constantsand Initial Value

1.3.1 Constants


1.3.2 Initial Value


2 Claimed/Expected Security Margins

3 Security Anaylsis

  • Best know attack: math by Wang
  • Best known collision example: 64-step collision by De Canniere and Rechberger

something like: best know attack to date: kind of attack, which variant has been looked at (e.g. round-reduced), complexity, and reference to paper and abstract.

may be make here a new page with the other cryptanalysis results.