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

4.1.7 Key Expansion (Keyexpansion Operation)

As previously mentioned, Keyexpansion refers to the process in which the 128 bits of the original key are expanded into eleven 128-bit round keys.

To compute round key (n+1) from round key (n) these steps are performed:

  1. Compute the new first column of the next round key as shown in Figure 4-7:
    GUID-AF0257D1-41C7-438D-9EDF-E7A90345055B-low.gifFigure 4-7 Expanding First Column of Next Round Key

    First, all bytes of the old fourth column must be substituted using the Subbytes operation. These four bytes are shifted vertically by one byte position and then XORed to the old first column. The result of these operations is the new first column.

  2. Calculate columns 2 to 4 of the new round key as shown:
    1. [new second column] = [new first column] XOR [old second column]
    2. [new third column] = [new second column] XOR [old third column]
    3. [new fourth column] = [new third column] XOR [old fourth column]

    Figure 4-8 illustrates the calculation of columns 2 to 4 of the new round key.

    GUID-242F2EAE-569D-43AE-96AB-4720026120A8-low.gifFigure 4-8 Expanding Other Columns of Next Round Key