Rosetta Xtra - Hash Functions

Hash functions are used to make "digital fingerprints" for strings and files. In network transfers for example, CRC32 ( Cyclic Redundancy Checksum ) is used to detect errors during transmission. While CRC32 can detect errors, just like MD5 can, the difference between the various hash functions lies in their ability to accurately detected authenticity. MD5 can better detect changes than CRC32. When speed is important, CRC32 is a much faster algorithm. Applications such as PKZip and Winzip uses CRC32 to calculate file authenticity.

The RSA MD5 Message Digest algorithm will convert files or strings of variable length into a handy 128 bit string reference. By changing a single character or byte in the source file will produce a completely different 128 bit string reference. The CRC32 algorithm converts file or strings to a handy 32 bit number, displayed in hexadecimal notation.

Some possible uses of hash functions are to:

1. Verifying the completeness of a downloaded file
2. Create "signatures" to passwords for higher security
3. Check for file differences
4. Check for file tampering
5. Check for the authenticity of a message

Method summary for Hash Algorithm

md5File()

crcFile()

md5String()

crcString()