3DES or the Triple Data Encryption Algorithm (TDEA) was
developed to address the obvious flaws in DES without
designing a whole new cryptosystem. Data Encryption
Standard (DES) uses a 56-bit key and is not deemed sufficient
to encrypt sensitive data. 3-DES simply extends the key size
of DES by applying the algorithm three times in succession
with three different keys. The combined key size is thus 168
bits (3 times 56). TDEA involves using three 64-bit DEA keys
(K1, K2, K3) in Encrypt-Decrypt- Encrypt (EDE) mode, that
is, the plain text is encrypted with K1, then decrypted with
K2, and then encrypted again with K3 [17]. The standards
define three keying options: