In general TDES with three different keys ( 3-key TDES ) has a key length of 168 bits : three 56-bit DES keys ( with parity bits 3-key TDES has the total storage length of 192 bits ) , but due to the meet-in-the-middle attack the effective security it provides is only 112 bits . In general Triple DES with three independent keys ( keying option 1 ) has 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 .