SLAU846A June 2023 – October 2023 MSPM0G1105 , MSPM0G1106 , MSPM0G1107 , MSPM0G1505 , MSPM0G1506 , MSPM0G1507 , MSPM0G3105 , MSPM0G3105-Q1 , MSPM0G3106 , MSPM0G3106-Q1 , MSPM0G3107 , MSPM0G3107-Q1 , MSPM0G3505 , MSPM0G3505-Q1 , MSPM0G3506 , MSPM0G3506-Q1 , MSPM0G3507 , MSPM0G3507-Q1
CTR-mode decryption of N blocks of ciphertext into N blocks of plaintext is achieved by following the same steps given for encryption (Section 23.2.7.5.1), but substituting the ciphertext for the plaintext and the reverse. Note that only the forward cipher is used in CTR mode; the encryption and decryption operations are identical and the same software implementation can be used for both, with substitution of ciphertext for plaintext in the case of decryption.