Patent attributes
Apparatus having corresponding methods and computer programs comprise: a key input module to receive a first cryptographic key; and a reverse key expansion module to generate a second cryptographic key based on the first cryptographic key, wherein each of the first cryptographic key and the second cryptographic key comprises a plurality of words, and wherein the reverse key expansion module comprises a first word module to generate the first word of the second cryptographic key based on the first word of the first cryptographic key and the last two words of the first cryptographic key, and a remaining word module to generate the remaining words of the second cryptographic key, the remaining word module comprising at least one word module to generate a word of the second cryptographic key based on the corresponding word, and the immediately previous word, of the first cryptographic key.