SI1034-A-GM 参数 Datasheet PDF下载

Si102x/3x

14.6.5. Counter Mode

The Counter (CTR) Mode uses a sequential counter which is incremented after each block. This turns the

block cipher into a stream cipher. This algorithm is shown inFigure 14.4. Note that the decryption operation

actually uses the encryption key and encryption block cipher. The XOR operation is always on the output

of the cipher. The counter is a 16-byte block. Often, several bytes of the counter are initialized to a nonce

(number used once). The last byte of the counter is incremented and propagated. Thus, the counter is

treated as a 16-byte big endian integer.

Encryption

Counter

(0x00...00)

Counter

(0x00...01)

Encryption Key

Encryption

Cipher

XOR

Encryption Key

Encryption

Cipher

XOR

Plaintext

Plaintext

Ciphertext

Ciphertext

Decryption

Encryption

Key

Ciphertext

Counter

(0x00...00)

Counter

(0x00...01)

Encryption

Cipher

XOR

Encryption

Key

Ciphertext

Encryption

Cipher

XOR

Plaintext

Plaintext

Figure 14.7. Counter Mode

Rev. 0.3

199