Security for Microsoft® Visual Basic® .NET

Hash Digests

As we mentioned earlier in this chapter, a hash is a type of one-way cryptography. Some people refer to hashing as encryption; others feel it’s not strictly encryption because the hash cannot be unencrypted. A hash is a very large number, generated by scrambling and condensing the letters of a string. In this chapter, you’ll use the SHA-1 algorithm. SHA-1 is an acronym for Secure Hashing Algorithm. The "-1" refers to revision 1, which was developed in 1994. SHA-1 takes a string as input and returns a 160-bit (20-byte) number. Because a string is being condensed into a fixed-size number, the result is called a hash digest, where digest indicates a shortened size, similar to Reader’s Digest condensed books. Hash digests are considered ...