SLAA547C July   2013  – July 2021 MSP430FR5739

 

  1. 1Software Benchmarks
    1. 1.1 AES Benchmarks
    2. 1.2 DES Benchmarks
    3. 1.3 SHA-2 Benchmarks
  2. 2Using Library Functions
    1. 2.1 AES 128
      1. 2.1.1 Encrypting With AES 128
      2. 2.1.2 Decrypting With AES 128
    2. 2.2 DES
      1. 2.2.1 Setting the Key Schedule for DES
      2. 2.2.2 Encrypting and Decryption With DES
      3. 2.2.3 Encryption and Decryption With DES CBC Mode
    3. 2.3 3DES
      1. 2.3.1 Encrypting and Decrypting With Triple DES
    4. 2.4 SHA-2
      1. 2.4.1 Hashing With SHA-256
      2. 2.4.2 Hashing With SHA-224
  3. 3Overview of Library Functions
    1. 3.1 AES 128
      1.      aes_enc_dec
      2.      aes_encrypt
    2. 3.2 DES and 3DES
      1.      Des_Key
      2.      Des_Enc
      3.      Des_Dec
      4.      DES_ENC_CBC
      5.      DES_DEC_CBC
      6.      TripleDES_ENC
      7.      TripleDES_DEC
      8.      TripleDES_ENC_CBC
      9.      TripleDES_DEC_CBC
    3. 3.3 SHA-256 and SHA-224
      1.      SHA_256
  4. 4Cryptographic Standard Definitions
    1. 4.1 AES
      1. 4.1.1 Basic Concept of Algorithm
      2. 4.1.2 Structure of Key and Input Data
      3. 4.1.3 Substitute Bytes (Subbytes Operation)
      4. 4.1.4 Shift Rows (Shiftrows Operation)
      5. 4.1.5 Mix Columns (Mixcolumns Operation)
      6. 4.1.6 Add Round Key (Addroundkey Operation)
      7. 4.1.7 Key Expansion (Keyexpansion Operation)
    2. 4.2 DES and 3DES
      1. 4.2.1 DES Algorithm Structure
      2. 4.2.2 The Function Block
      3. 4.2.3 Key Schedule
      4. 4.2.4 Triple DES
      5. 4.2.5 Cipher Block Chaining (CBC) Mode
    3. 4.3 SHA-256 and SHA-224
      1. 4.3.1 Message Padding and Parsing
      2. 4.3.2 SHA-256 Algorithm
      3. 4.3.3 Equations Found in SHA-256 Algorithm
      4. 4.3.4 SHA-224
  5. 5References
    1.     Revision History

4.2.3 Key Schedule

The key schedule for all sixteen rounds of the DES algorithm must be calculated before encryption or decryption can occur. The key schedule process in this library is the most CPU intensive component of the algorithm. System speed can be increased by limiting the number of keys to be scheduled. Figure 4-11 describes how the key schedule is calculated. First, the 64-bit key is sent through a permutation box that reduces the bit count to 56. The result is split evenly and left rotated by 1-2 bits depending on the round. The rotate results are fed into a second permutation box that gives the round key used in the DES Function block.

GUID-97F8223C-58E9-4CDB-810C-494243B85C36-low.gifFigure 4-11 Key Schedule Function Diagram