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2

"In software" means programming the cipher on a multifunctional processor or smart chip. The normal instruction set is used to build the algorithm, and not available operations have to be emulated. "In hardware" means building the cipher in real hardware, like on a Field-programmable gate array (FPGA) or Application-specific integrated circuit (ASIC). ...

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"Software" in this case generally refers to software with few threads, but possibly quite a lot of memory accesses/bandwidth required. Memory bandwidth is expensive in die area, so hardware isn't suited to things that use tons of memory. eg scrypt requires quite a lot of memory, bcrypt makes a lot of data-dependent memory reads, etc. You CAN make hardware to ...

5

XSalsa20 uses the same cryptographic core as Salsa20 and comes with a security proof that it's secure if Salsa20 is secure. It doesn't use the core of ChaCha and thus has worse diffusion. The way XSalsa20 works is that it hashes its 256 bit key and the first 128 bits of the nonce using HSalsa down to a 256 bit key and then uses that key together with the ...

1

I suggest Vigenère cipher, it is fun on paper and also you can be creative in using key. you can use your phone number as key or your entire family phone number in age order. Key: ABCDABCDABCDABCDABCDABCDABCD Plaintext: CRYPTOISSHORTFORCRYPTOGRAPHY Ciphertext: CSASTPKVSIQUTGQUCSASTPIUAQJB http://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher

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For confidentiality purposes? one time pad (when possible) rc4 (because you can by hand)

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It depends on the exact Merkle-Damgaard hash. MD5 will literally take an arbitrary length; that's because the value placed in the padding is actually computed modulo $2^{64}$. For SHA-1 and the SHA-2 hashes, yes, you are correct; there is an upper bound on the length of the preimages that could potentially be hashed; for SHA-1, SHA-224 and SHA-256, it's ...

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Normally, questions like this are considered off-topic; however, in this case, I can give a quick answer -- it's RC4

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You can find a very illustrative explanation of how not to teach yourself crypto here: http://outsourcedbits.org/2014/11/11/how-not-to-learn-cryptography/ Briefly the exciting field of crypto includes an intersection of computer science, math and engineering. The latter is not required always if you are interested in a scientific path

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It will depend entirely on the specific encryption scheme. There is really no theoretical reason why a ciphertext should not be clearly identifiable as being a ciphertext and not a plaintext. In fact, take any encryption scheme and modify it so that the encryption algorithm works as before, only it appends to the ciphertext the string "THIS IS A ...

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