Si102x/3x
14.3. AES Block Cipher
The basic AES Block Cipher is the basic encryption/decryption algorithm as defined by the NIST standard.
A clock cipher mode is a method of encrypting and decrypting one block of data. The input data and output
data are not manipulated, chained, or exclusive ORed with other data. This simple block cipher mode is
sometimes called the Electronic Code Book (ECB) mode. This mode is illustrated in Figure 14.3
Each operation represents one block (sixteen bytes) of data. The plaintext is the plain unencrypted data.
The ciphertext is the encrypted data. The encryption key and decryption keys are symmetric. The decryp-
tion key is the inverse key of the decryption key. Note that the Encryption operation is not the same as the
decryption operation. The two operations are different and the AES core operates differently depending on
whether encryption or decryption is selected.
Note that each encryption or decryption operation is independent of other operations. Also note that the
same key is used over and over again for each operation.
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