# Tag Info

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Ciphers (enciphering arbitrary length data, probably a lot): As you want the cipher resulting being realistic, it must meet some performance criteria. Often assembler instructions involved are took into account in designing professional ciphers. So C and be prepared to peer at assembly result given by the compiler. Speed is not ignored in general, although ...

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If anyone needs it, C# code to calculate the KCV (you need only the first three bytes of the GetKcv return value): class Aes { private readonly byte[] _iv; private readonly int _secretLength; private readonly byte[] _secret; private readonly RijndaelManaged _cryptoEngine; public Aes() { _iv = new byte[] { 0, 0, 0, 0, 0, 0, ...

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To calculate the KCV for AES, you take the first three bytes of the encryption of zero under your key. Indeed, the case you've given is precisely this - the zero vector encrypted under the key 48C3B4286FF421A4A328E68AD9E542A4 is 77dc841daeb43315fed9acdf2f965f45, which restricts to 77dc84. In your question you say you already have AES-128 encryption, at ...

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What the specification is saying is that prior to processing, the message is padded to a full block length, with the empty message padded to a single block. The spec on page 4 describes the input into the algorithm as: Define $||a||_n = max\{1, \lceil|a|/n\rceil \}$, where the empty string counts as one block Let $m = ||M||_n$ Partition $M$ into \$M[1] ... ...

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Some implementations of RSA PKCS#1v1.5 use message recovery to find out which hash function was applied. PKCS#11 API defines the C_SignRecover and C_VerifyRecover and allow them to be used with the most RSA mechanisms. Long story short: this means that there is very widely available API which allows the functionality. Thus, it is likely that quite a few ...

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A signature scheme with message recovery is standardized as ISO/IEC 9796-2 (link to preview). Scheme 1 in this standard is commonly used in the Smart Card industry, despite its known weaknesses in a chosen-message setup. Example real-life uses include the EMV banking application (the free documents linked there include a description of an industry-standard ...

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