What is TripleDES?

TripleDES (3DES or TDEA) is a block cipher that applies the DES algorithm three times to each data block. It was designed to extend the life of DES when its 56-bit key became too weak. TripleDES supports 168-bit effective key length (or 112 bits in two-key mode). Still used in legacy systems and some payment card standards, TripleDES is being phased out in favor of AES. NIST has deprecated 3DES for new applications since 2017.