C.I.E – Carta di Identità Elettronica Functional Specification Version 2.0
CIE - Functional Specification v 2.0
CIE - Functional Specification v 2.0
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• a sequence of q cipher text blocks C 1 , C 2 , …, C q each of 64 bitsP 1P 2P qSV++...+ENC KENC K...ENC KC 1C 2...C qFigure 4: CBC enciphering schemeIn case of data encryption, the output is the string C obtained by chaining C 1 ,C 2 ,...,C q .In case of MAC computation, the output is the last block (C q ).The consequent deciphering operation is:C 1C 2C qDEC KDEC K...DEC KSV++...+P 1P 2...P qFigure 5: CBC deciphering scheme13.2.4 MAC3The MAC3 (Message Authentication Code) is a key-dependent one-way hash function. Thismechanism is very useful to provide authenticity without secrecy. It uses a symmetric-keyalgorithm with a 16 or 24 bytes key.The following figure shows the scheme of MAC 3. The SV is a string of 64-bit all set to 0.CIE - <strong>Functional</strong> <strong>Specification</strong> v <strong>2.0</strong> -Page 75/76