# Why are there so many versions of the TEA block cipher?

Why are there so many types of TEA, for example TEA, XTEA, and XXTEA? What are the differences?

• Note: the two XXTEA attacks referred to in the answer are the same. Addition: one of XXTEA's feature is a block size parameter. However the algorithm's reduction in the number of rounds as the block size grows is too aggressive, making it vulnerable to differential cryptanalysis, with an attack for $2^{59}$ chosen plaintexts when the block is widened from 8 to 212 bytes or more. I know no published attack for less, and it would require a major advance to break XXTEA with a block size of 8 to 24 bytes, or if it was strengthened by replacing 6 with 12 in the formula for the number of rounds. – fgrieu Sep 17 '18 at 5:46