Topic Path: Symbol Reference > Classes > TIdHashSHA1 Class
TIdHashSHA1 Class

Implements a hashing class for the Secure Hash Algorithm 1 (SHA1).

TIdHashSHA1 = class(TIdHash160);

TIdHashSHA1 is a TIdHash160 descendant that implements the Secure Hash Algorithm 1 (SHA1), as described in the Internet Standards documents: 

RFC 3174 - US Secure Hash Algorithm 1 (SHA1)  

TIdHashSHA1 is based on principles similar to those used by Professor Ronald L. Rivest of MIT when designing the MD4 message digest algorithm, as described in the Internet Standards documents: 

RFC 1320 - The MD4 Message-Digest Algorithm  

RFC 1321 - The MD5 Message-Digest Algorithm  

TIdHashSHA1 implements the Secure Hash Algorithm 1 (SHA1) which computes a condensed representation of a message or a data file, and produces a 160-bit output called a message digest. The message digest be input to a signature algorithm which generates or verifies the signature for a message. 

SHA1 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. 

TIdHashSHA1 extends the ancestor class by providing an overridden HashValue method that implements the SHA1 algorithm. TIdHashSHA1 also includes protected members and methods required to manage the buffer and checksum values required for the algorithm.

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