DES3 in CBC mode Encryption/Decryption

Triple-DES has a key length of 168-bits (three 56-bit DES keys), but because of the meet-in-the-middle attack it has an effective key size of 112 bits. With the 24 parity bits (8 parity bits per DES key), Triple-DES has a total storage length of 192 bits. A variant, called two-key triple-DES, uses k1 = k3, thus reducing the key size to 112 bits and the storage length to 128 bits. However, this mode is susceptible to certain chosen-plaintext or known-plaintext attacks [1] [2]. These attacks are highly impractical, but they are a weakness of this variant.