Internet of Things for Architects

Symmetric cryptography

In encryption, plaintext refers to the unencrypted input and the output is called ciphertext, as it is encrypted. The standard for encryption is the Advanced Encryption Standard (AES) which replaced older DES algorithms dating from the 1970s. AES is part of the FIPS specification and the ISO/IEC 18033-3 standard used worldwide. AES algorithms use fixed blocks of 128, 192, or 256 bits. Messages larger than the bit width will be split into multiple blocks. AES has four basic phases of operation during the cipher. The pseudo code for a generic AES encryption is shown here:

// Psuedo code for an AES-128 Cipher// in: 128 bits (plaintext)// out: 128 bits (ciphertext)// w: 44 words, 32 bits each (expanded key)state = inw=KeyExpansion(key) ...