I intend to use Crypto++ for encrypting audio recording files. A file needs to be played back in a random access way, setting the play cursor at any time of the recording. I chose AES-CTR because it is seekable. So I need to calculate the index of the block at, e.g. 0h:35m and start decrypting. That time pont is the index=131250 AES block. The key is known and the first-block IV too. My questions: - Is the reasoning above right ? - what is the "counter increment" formula used by Crypto++ in CTR mode for the updated vector to be used in AES ? It's just incrementing by one the 16-byte unsigned integer vector at each new block with wrap around in the event of carry in the MSBit ? - Does Crypto++ has an utility to add a number to an array representing a 16-byte unsigned integer? What is recommended for that?
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