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XSL on serpent and rijndael - which is most affected?

So I've often looked at serpent and thought it was a very strong contender in AES. Not so long ago I was looking for evidence as to why it didn't beat rijndael. So far, the closest I've got answering that is this: The 32 rounds means that Serpent…
user46
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How does a certificate authority issue a digital certificate?

I am new to cryptography and I want to know the details of how a Certificate Authority issues a digital certificate. From what I know (please correct me if I'm wrong at any parts of my explanation): If Alice wants to request a digital certificate,…
user2935569
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Under what conditions did a Bletchley bombe stop?

I am trying to understand the conditions necessary for one of the Bletchley Park bombes to stop. Let me give an example. I have been experimenting with Enigma machine and bombe simulators to try to understand better how the bombe works. Using a…
Geoff
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Probability of SHA256 Collisions for Certain Amount of Hashed Values

I wonder if you can help me figure out that question: Is there a known probability function f: N -> [0,1], that computes the probability of a sha256 collision for a certain amount of values to be hashed? The values might fulfill some simplicity…
vern
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How to use RCON In Key Expansion of 128 Bit Advanced Encryption Standard

I have a question about RCON here is my illustration... this is the 128 bit key.. [2b] [28] [ab] [09] [7e] [ae] [f7] [cf] [15] [d2] [15] [4f] [16] [a6] [88] [3c] and then I will get this.. [09] [cf] [4f] [3c] and then I will put down the first…
goldroger
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Why are the outputs of the md5sum tool and Crypto++'s MD5 different?

Could you please tell me what is the difference of coreutils' md5sum and sha*sum tools (sha1sum, sha224sum, etc.) compared to Crypto++'s digest functions? I've written a piece of code using Crypto++ hash functions but the result is different from…
SP5RFD
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Deterministic nonces in CTR mode

I want to encrypt a file with AES in CTR mode. I have a 256 bit master key and the file. Given these, the encryption must be deterministic, so I can't use a random nonce in the usual way. Fortunately the master key will be unique¹. My original plan…
CodesInChaos
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What are advantages of using a HMAC over RSA with SHA-1 hashes?

I am currently studying for an exam and this was a previous question: Give one advantage of using HMACs over using RSA to sign SHA-1 hashes. My thoughts are that it has something to do with the fact that HMAC assumes a private key has already been…
Shane
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Why does a broken hash function undermine an HMAC?

For instance, what makes MD4 a bad choice for an HMAC? In this case I am asking about MD4 because its less than ideal. I know that a preimage attack can be used to undermine the system, but why? What is the attacker calculating?
Rook
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Does encrypting twice using the same block cipher produce a security weakness?

If I use the output of a cipher, for example a block cipher such as AES and encrypt it again with the same algorithm, I read that this introduces weaknesses into the overall security of the system. Is this the case?
rezx
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Does using modulo (%) affect quality of randomness?

I'm writing a small script that generates random non-signed decimal integers within a certain range of values. I'm using GNU od, with the following command: od /dev/hwrng --address-radix=n --read-bytes=4 --format=u4 /dev/hwrng is linked to a SoC…
user21698
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Cryptographic security of PHP mt_rand() function using Mersenne Twister algo

At StackOverflow, this question has been asked. It uses additional random entropy and a hash method (among others) to try and create a cryptographically secure pseudo-random number generator for PHP. PHP seems to use a Mersenne Twister algorithm…
Maarten Bodewes
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How are random numbers for RSA generated?

The RSA public key encryption requires two very large prime numbers as part of its encryption process that serve as secrets. These are typically generated with cryptographically secure random number generators of some kind. However, random number…
Billy ONeal
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RFC 6979 - Why not simply hash the message & the private key for deterministic ECDSA?

Why go through the trouble of using the HMAC_DRBG process, instead of simply hashing [message | private key] to calculate $k$ for deterministic ECDSA? If the resulting $k$ or the signature is invalid, then a known byte value can be appended to the…
thera
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What does "circuits" mean in Cryptography?

I am not a hardcore cryptographer so this might be a really stupid question. I am looking through some papers in homomorphic encryption and discovered they describe computation as "circuits", why do they use this particular term? Isn't algorithm a…
Boyu Fang
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