Hashes

Hash values are used in computer security in order to encrypt text. Hashes are the result of a mathematical algorithms applied to data or text. The formula takes texts and produces a smaller string to text. This string of text does not contain part of the original document and appears to be a random string of letters and numbers. However the hash value is not random as it is produced by an algorithm. The hash is unique to each document; therefore it is highly unlikely that multiple documents, no matter how similar, will not produce the same hash value. The significant changing of the hash value as a result of a minute change to the data itself is referred to as the “avalanche effect”. The avalanche effect is desirable as long as the algorithm has a strong randomization. If a small change in the text does not produce significant change in the hash value, the cryptography is weak and could possibly be cracked.
 * Hashes **

To ensure that data is received unchanged, a sender can send the hash value with the document. When the message is received, the receiver can get the hash value same document. If the two values are the same, then the document has not been changed. If the values differ, even slightly, the document has been changed.

Examples of hash algorithms include SHA-1 and MD5. Secure hash algorithm 1, or SHA-1, was developed by the National Security Agency (NSA) in 1995. This particular algorithm produces a 160-bit hash value. Message-Digest algorithm 5 (MD5) was created by Ron Rivest in 1991. In 2005, weaknesses were identified with SHA-1.

MD-5 produces a 128-bit hash value. MD5 typically produces a 32 digit hexadecimal number for the hash. Vulnerabilities to MD-5 include publications of rainbow tables that can be used to reverse some MD5 hashes.