3 DES (Triple DES): Was developed to extend life of DES systems while getting ready for AES.
Symmetric – 64-bit block cipher – 56-bit key, 16 rounds of encryption, uses Fistel. 3 rounds of DES
vs 1. K1 (keymode1) – 3 different keys with a key length of 168-bits (three 56-bit DES keys), but
due to the meet-in-the-middle attack, the effective security it provides is only 112-bits.