XXTEA

XXTEA, also called Corrected Block TEA, is a block cipher designed by Roger Needham and David Wheeler of the Cambridge Computer Laboratory to correct weaknesses in their earlier Block TEA. It was presented in an unpublished technical report in October 1998 and is not subject to any patents. It is an unbalanced Feistel network that works on variable-length blocks of any multiple of 32 bits with a minimum of 64 bits, and it runs at least six full cycles, rising to 32 for small blocks. Its round function uses both neighbours of each word, which gives faster diffusion than Block TEA. Because the code is so small it suits microcontrollers with very little memory. A chosen-plaintext attack published in 2010 by E. Yarrkov breaks the wide-block form of the full cipher with about 2 to the 59th queries, so it is not considered strong by current standards.