DES (Data Encryption Standard) Cipher Algorithm

This section describes DES (Data Encryption Standard) algorithm - A 16-round Feistel cipher with block size of 64 bits.

DES Cipher - A 16-round Feistel cipher with block size of 64 bits. DES stands for Data Encryption Standard.

DES was developed by IBM in 1974 in response to a federal government public invitation for data encryption algorithms. In 977, DES was published as a federal standard, FIPS PUB 46.

DES algorithm:

Input: 
   T: 64 bits of clear text
   k1, k2, ..., k16: 16 round keys
   IP: Initial permutation
   FP: Final permutation
   f(): Round function
   
Output: 
   C: 64 bits of cipher text

Algorithm:
   T' = IP(T), applying initial permutation
   (L0, R0) = T', dividing T' into two 32-bit parts
   (L1, R1) = (R0, L0 ^ f(R0, k1))
   (L2, R2) = (R1, L1 ^ f(R1, k2))
   ......
   C' = (R16, L16), swapping the two parts
   C = FP(C'), applying final permutation

where ^ is the XOR operation.

The round function f(R,k) is defined as:

Input: 
   R: 32-bit input data
   k: 48-bit round key
   E: Expansion permutation
   P: Round permutation
   s(): S boxes function
   
Output
   R' = f(R,k): 32-bit output data

Algorithm
   X = E(R), applying expansion permutation and returning 48-bit data
   X' = X ^ k, XOR with the round key
   X" = s(X'), applying S boxes function and returning 32-bit data
   R' = P(X"), applying the round permutation

The S boxes function s(X) is defined as:

Input: 
   X: 48-bit input data
   S1, S2, ..., S8: 8 S boxes - 4 x 16 tables

Output: 
   X' = s(X): 32-bit output data

Algorithm: 
   (X1, X2, ..., X8) = X, dividing X into 8 6-bit parts
   X' = (S1(X1), S2(X2), ..., S8(X8))
      where Si(Xi) is the value at row r and column c of S box i with
         r = 2*b1 + b6 
         c = 8*b2 + 4*b3 + 2*b3 + b4 
         b1, b2, b3, b4, b5, b6 are the 6 bits of the Xi 

DES cipher algorithm supporting tables:

Initial Permutation - IP:

58    50   42    34    26   18    10    2
60    52   44    36    28   20    12    4
62    54   46    38    30   22    14    6
64    56   48    40    32   24    16    8
57    49   41    33    25   17     9    1
59    51   43    35    27   19    11    3
61    53   45    37    29   21    13    5
63    55   47    39    31   23    15    7

Final Permutation - FP:

40     8   48    16    56   24    64   32
39     7   47    15    55   23    63   31
38     6   46    14    54   22    62   30
37     5   45    13    53   21    61   29
36     4   44    12    52   20    60   28
35     3   43    11    51   19    59   27
34     2   42    10    50   18    58   26
33     1   41     9    49   17    57   25

Expansion permutation - E:

32     1    2     3     4    5
 4     5    6     7     8    9
 8     9   10    11    12   13
12    13   14    15    16   17
16    17   18    19    20   21
20    21   22    23    24   25
24    25   26    27    28   29
28    29   30    31    32    1

Round permutation - P:

16   7  20  21
29  12  28  17
 1  15  23  26
 5  18  31  10
 2   8  24  14
32  27   3   9
19  13  30   6
22  11   4  25

S boxes - S1, S2, ..., S8:

                        S1

14  4  13  1   2 15  11  8   3 10   6 12   5  9   0  7
 0 15   7  4  14  2  13  1  10  6  12 11   9  5   3  8
 4  1  14  8  13  6   2 11  15 12   9  7   3 10   5  0
15 12   8  2   4  9   1  7   5 11   3 14  10  0   6 13

                        S2

15  1   8 14   6 11   3  4   9  7   2 13  12  0   5 10
 3 13   4  7  15  2   8 14  12  0   1 10   6  9  11  5
 0 14   7 11  10  4  13  1   5  8  12  6   9  3   2 15
13  8  10  1   3 15   4  2  11  6   7 12   0  5  14  9

                        S3

10  0   9 14   6  3  15  5   1 13  12  7  11  4   2  8
13  7   0  9   3  4   6 10   2  8   5 14  12 11  15  1
13  6   4  9   8 15   3  0  11  1   2 12   5 10  14  7
 1 10  13  0   6  9   8  7   4 15  14  3  11  5   2 12

                        S4

 7 13  14  3   0  6   9 10   1  2   8  5  11 12   4 15
13  8  11  5   6 15   0  3   4  7   2 12   1 10  14  9
10  6   9  0  12 11   7 13  15  1   3 14   5  2   8  4
 3 15   0  6  10  1  13  8   9  4   5 11  12  7   2 14

                        S5

 2 12   4  1   7 10  11  6   8  5   3 15  13  0  14  9
14 11   2 12   4  7  13  1   5  0  15 10   3  9   8  6
 4  2   1 11  10 13   7  8  15  9  12  5   6  3   0 14
11  8  12  7   1 14   2 13   6 15   0  9  10  4   5  3

                        S6

12  1  10 15   9  2   6  8   0 13   3  4  14  7   5 11
10 15   4  2   7 12   9  5   6  1  13 14   0 11   3  8
 9 14  15  5   2  8  12  3   7  0   4 10   1 13  11  6
 4  3   2 12   9  5  15 10  11 14   1  7   6  0   8 13

                        S7

 4 11   2 14  15  0   8 13   3 12   9  7   5 10   6  1
13  0  11  7   4  9   1 10  14  3   5 12   2 15   8  6
 1  4  11 13  12  3   7 14  10 15   6  8   0  5   9  2
 6 11  13  8   1  4  10  7   9  5   0 15  14  2   3 12

                        S8

13  2   8  4   6 15  11  1  10  9   3 14   5  0  12  7
 1 15  13  8  10  3   7  4  12  5   6 11   0 14   9  2
 7 11   4  1   9 12  14  2   0  6  10 13  15  3   5  8
 2  1  14  7   4 10   8 13  15 12   9  0   3  5   6 11

Table of Contents

 About This Book

 Cryptography Terminology

 Cryptography Basic Concepts

 Introduction to AES (Advanced Encryption Standard)

Introduction to DES Algorithm

 What Is Block Cipher?

DES (Data Encryption Standard) Cipher Algorithm

 DES Key Schedule (Round Keys Generation) Algorithm

 DES Decryption Algorithm

 DES Algorithm - Illustrated with Java Programs

 DES Algorithm Java Implementation

 DES Algorithm - Java Implementation in JDK JCE

 DES Encryption Operation Modes

 DES in Stream Cipher Modes

 PHP Implementation of DES - mcrypt

 Blowfish - 8-Byte Block Cipher

 Secret Key Generation and Management

 Cipher - Secret Key Encryption and Decryption

 Introduction of RSA Algorithm

 RSA Implementation using java.math.BigInteger Class

 Introduction of DSA (Digital Signature Algorithm)

 Java Default Implementation of DSA

 Private key and Public Key Pair Generation

 PKCS#8/X.509 Private/Public Encoding Standards

 Cipher - Public Key Encryption and Decryption

 MD5 Mesasge Digest Algorithm

 SHA1 Mesasge Digest Algorithm

 OpenSSL Introduction and Installation

 OpenSSL Generating and Managing RSA Keys

 OpenSSL Managing Certificates

 OpenSSL Generating and Signing CSR

 OpenSSL Validating Certificate Path

 "keytool" and "keystore" from JDK

 "OpenSSL" Signing CSR Generated by "keytool"

 Migrating Keys from "keystore" to "OpenSSL" Key Files

 Certificate X.509 Standard and DER/PEM Formats

 Migrating Keys from "OpenSSL" Key Files to "keystore"

 Using Certificates in IE (Internet Explorer)

 Using Certificates in Firefox

 Using Certificates in Google Chrome

 Outdated Tutorials

 References

 PDF Printing Version