A symmetric encryption algorithm designed by Bruce Schneier in 1993 as an alternative to existing encryption algorithms, such as DES. Blowfish is a 64-bit block cipher (i.e., a cryptographic key and algorithm are applied to a block of data rather than single bits) that uses a key length that can vary between 32 and 448 bits. Blowfish is available for free use by any, and the technology is not patented and free of license.