Java Glossary : SHA-1

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Secure Hash Algorithm 1, a message-digest algorithm developed by NIST the National Institute of Standards and Technology and NSA the National Security Agency. SHA-1 produces an 160-bit (20 byte) message digest used for creating unforgeable digital signatures. The algorithm is slower than MD5, but the message digest is larger, which makes it more resistant to brute force attacks, which choose messages at random in an attempt to generate the same message digest. SHA-1 is also used to digitally sign jar files. PGP uses SHA-1 for digitally signing email. You compute it using a MesssageDigest object created like this:

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Note that SHA-1 involves no private or public key. The algorithm for computing it is completely public. It represents a summary of an entire file or message. Only that summary needs to be digitally signed/encrypted, not the entire file. SHA-1 now has higher strength brothers, SHA-256, SHA-384, and SHA-512 for 256, 384 and 512-bit digests respectively.

The SHA-1 digests that you see in the manifest of a digitally signed jar file are base64 encoded.

base64 ¤ certificate ¤ digest ¤ digital signing ¤ manifest ¤ MD5 ¤ PGP

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