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Synchronous stream cipher, or just stream cipher. In a synchronous stream cipher a stream of pseudo-random digits is generated independently of the plaintext and ciphertext messages, and then combined with the plaintext (to encrypt) or the ciphertext (to decrypt). In the most common form, binary digits are used (bits), and the keystream is combined with ...


3

Lots of problems are hard to solve but easy to check. For example: finding hash pre-images of particular values such as 0 calculating discrete logs of small numbers modulo a prime finding the factors of a large composite of a special form like $2^p-1$ I don't think there's an essential difference between solving and checking they're just arbitrary ...


3

Your key only seems to consist of n, which should be easily brute forced. So not very secure is the only answer that can be given. n could be very large (a 128 bit number or so), but in that case this scheme seems very inefficient. Please note the remarks on this kind of generator here and here. So even if it is secure, it may be very tricky to show that it ...


2

Since it's a linear cipher, you should be wary about a guessable padding, otherwise if your last block is only one char long, you will reveal almost your whole matrix on this last block. If you're too afraid of mangling the last word, use something like 'Z'+(random chars). But I really would not use any predictable padding with such a cipher.


2

I need a small clarification that why openssl using SHA1 in ECC when I am using secp384r1 curve, but in rfc they are saying we should use SHA2. OpenSSL uses SHA-1 because RFC 4492 defines the use of ECC on SSL with SHA-1. It should also support SHA-384 as defined in RFC 5289. Which hash algorithm is used in TLS depends on the cipher suite. For example: ...


1

If your environment was fully compromised you could at no point actually decrypt your data, defeating the purpose. So I’m going to assume the user only uses an authentic client and the client’s memory is protected during execution. Generate a private/public keypair. Store the public key on the server, encrypt the private key with the user’s passphrase and ...


1

What you ask for is possible, but only (I'm pretty certain, although I don't have any sort of formal proof) if there is a central authority who has a separate, secured connection to each user. Also, the concept of public keys becomes unnecessary. If the encryption and decryption key is a function of "public keys", then any user who at any point was a member ...



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