TDES is a symmetric key-block cipher which applies DES (Data Encryption Standard) three times with three different keys (k1, k2, k3). Like DES, the TDES structure is based on Feistel scheme.

• Encryption

Let:

• S be a block of 64 bits size clear message
• E(k,S) be an encrypting function with the key k
• D(k,S) a decrypting function with the key k
• k1, k2 and k3; three different keys (56 bits size each + 8 parity bits)

TDES(S)= E(k3,D(k2,E(k1,S))). (Encrypt with k1; Decrypt with k2 and Encrypt again with k3. The total key size is 112 bits).

• Decryption

Decryption is the reverse operation:

Let C be the ciphertext obtained through the TDES operation.

S = D(k1,E(k2,D(k3,C))). (Decrypt with k3; Encrypt with k2 and Decrypt with k1).

• More information on encrypting / decrypting can be found on wikipedia: https://en.wikipedia.org/wiki/Triple_DES#Security

• 1. Download the program.
• 2. Open a terminal, go to the program folder.
• 3. Type "make" to run the makefile program (compilation program).
• 4. Type "./exe" to run the program and follow the instruction.

THE SOFTWARE IS UNDER MIT LICENSE AND IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND !!! TDES IS OFFICIALLY BEING RETIRED !!! THIS PROGRAM IS INTENDED FOR EDUCATIONAL PURPOSE, NOT FOR INDUSTRIAL USE !!!

MORE INFORMATION HERE: https://www.cryptomathic.com/news-events/blog/3des-is-officially-being-retired