Triple DES | Triple DES with 2 keys | Triple DES with 3 keys | Data Encryption Standard | Multiple DES

Introduction

DES is a symmetric block cipher (shared secret key), it uses a key length of 56-bits.

In Triple DES, each of the three rounds can be performed either encryption or decryption process using DES algorithm. It generates eight different possible modes for Triple DES. Triple DES is stronger than single DES because it performs more rounds of encryption.

Triple DES encrypts input data three times. The three keys are referred to as K1, K2 and K3.

Triple DES works with two ways:

Triple DES with 3 Keys

Encryption

Triple DES performs the same operation as double DES. Triple DES using three keys K1, K2 & K3 while encrypting plain text.

First it performs encryption on plaintext P, which is encrypted using K1 and obtains first cipher text C1.

Again, this cipher text is encrypted using key K2 which obtain the second cipher text C2.

Which is again encrypted using K3 & generate final cipher text C3.

Figure: Triple DES encryption using 3 keys

Decryption

Decryption of Triple DES is reverse of encryption.

In triple DES decryption process final cipher text C3 decrypt using K3, result is cipher text C2.

C2 will be decrypt with K2 and get C1 cipher text.

Then C1 cipher text decrypt with K1 key and get original plain text P.

Figure: Triple DES decryption using 3 keys

Triple DES with 2 Keys

Encryption

Triple DES performs the same operation as double DES.

Triple DES using two keys K1 & K2 while encrypting plain text.

First it performs encryption on plaintext P, which is encrypted using K1 obtains first cipher text C1.

Again, this cipher text is encrypted using key K2 which obtain the second cipher text C2.

Which is again encrypted using K1 & generate final cipher text C3.

Figure: Triple DES encryption using 2 keys

Decryption

Decryption of Triple DES is reverse of encryption.

In triple DES decryption process final cipher text C3 decrypt using K1, result is cipher text C2.

C2 will be decrypt with K2 and get C1 cipher text.

Then C1 cipher text decrypt with K1 key and get original plain text P.

Figure: Triple DES decryption using 2 keys

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