What is SHA-1?
--------------
SHA-1SUM is a small utility that allows you to calculate checksums of
any file using the Secure Hash Algorithm, like the "MD5 Message Digest
Algorithm", but SHA-1 is more secure. It is written in 100% assembly,
because it's very fast. (2MB file length, 3 seconds on a 68040/25.)
The algorithm taken from Federal Information Processing Standards
Publication 180-1, and tested with three examples described in this
material. You can check this on:
http://www.dice.ucl.ac.be/crypto/standards/fips/html/fip180-1.htm
Usage:
------
SHA-1SUM <filename>
Notes:
------
The program reads the whole file into the memory, that's why there
must be as much free RAM as long the file is.
Lay András <lay@dspnet.hu>
Some words from FIP180-1:
-------------------------
The Secure Hash Algorithm (SHA-1) is required for use with the Digital
Signature Algorithm (DSA) as specified in the Digital Signature
Standard (DSS) and whenever a secure hash algorithm is required for
federal applications. For a message of length < 2^64 bits, the SHA-1
produces a 160-bit condensed representation of the message called a
message digest. The message digest is used during generation of a
signature for the message. The SHA-1 is also used to compute a message
digest for the received version of the message during the process of
verifying the signature. Any change to the message in transit will,
with very high probability, result in a different message digest, and
the signature will fail to verify.
The SHA-1 is designed to have the following properties: it is
computationally infeasible to find a message which corresponds to a
given message digest, or to find two different messages which produce
the same message digest.
The SHA-1 is called secure because it is computationally infeasible to
find a message which corresponds to a given message digest, or to find
two different messages which produce the same message digest. Any
change to a message in transit will, with very high probability,
result in a different message digest, and the signature will fail to
verify. SHA-1 is a technical revision of SHA (FIPS 180). A circular
left shift operation has been added to the specifications in section
7, line b, page 9 of FIPS 180 and its equivalent in section 8, line c,
page 10 of FIPS 180. This revision improves the security provided by
this standard. The SHA-1 is based on principles similar to those used
by Professor Ronald L. Rivest of MIT when designing the MD4 message
digest algorithm ("The MD4 Message Digest Algorithm," Advances in
Cryptology - CRYPTO '90 Proceedings, Springer-Verlag, 1991, pp.
303-311), and is closely modelled after that algorithm.
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