Tiny Encryption Algorithm

The Tiny Encryption Algorithm, or TEA is a cipher designed for small size and easy software implementation. It is a Feistel cipher with 64-bit blocks, a 128-bit key, 32 rounds and a very simple round function using only 32-bit operations &mdash; addition, bitwise XOR and shift. In C, the encryption and decryption routines are under 10 lines each. No S-boxes are used, so the data space required is also tiny.

TEA has some weaknesses. Equivalent keys are one problem; each key is equivalent to three others, so the effective key size is only 126 bits. As a result, TEA is weak if used to build a cryptographic hash. This weakness led to a method for hacking Microsoft's Xbox game console, where the cipher was used as a hash function. TEA is also susceptible to a related-key attack which requires 223 chosen plaintexts under a related-key pair, with 232 time complexity .

Partly because of these weaknesses, a number of revisions of TEA have been designed. Block TEA or XTEA extends TEA to build a variable block size cipher. XXTEA is a later revision.

The cipher is freely available for any use. It has a home page; see external links.