Latest Crypto related questions

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alphazwest avatar
Decrypting Mono-Alphabetic Substitution Ciphertext
pr flag

I am reading Introduction to Modern Cryptography 3rd Edition (Google Books Preview of Relevant section, pages 10-11) and am struggling to understand the description of an attack method on a monoalphabetic substitution cipher.

It seems to be an improved version of a letter-frequency analysis approach, eliminating the need to "check what makes sense" manually. Some given information:

  1. All letters of the ...
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ezio avatar
Why do we need to use Asymmetric cryptography if Diffie-Hellman solves the key exchange problem of symmetric cryptography?
cn flag

I am new to cryptography and I cant get my head around this issue:

If symmetric cryptography is faster then asymmetric and given that Diffie-Hellman key exchange algorithm allows you to exchange keys safely why bother using Asymmetric cryptography if I can exchange symmetric keys safely ?

Score: 0
Joseph Carpenter avatar
Storing 4 char prefix for 32bit hex token after storing HMAC digest
us flag

Currently I am working on a public api that uses token authentication. The token is a 32 bit random hex that is shared with the user and then stored in our database as an HMAC digest using a secret key. The token is not stored except for the first 4 characters.

My question is, is it safe to store the prefix like this?

My intuition tells me that it is not safe as it gives any attacker the beginning o ...

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Multi key layered encryption verification
us flag

Is it possible to take some value text like “Hello World!” And encrypt it with a random key. Then take the encrypted message and encrypt it again with another random key. And so on…

Then can you write a function that takes in the final encrypted message plus any one of the keys from before and return True or False. With True being: the key was used to encrypt the message. And False being: t ...

Score: 0
juanmf avatar
RSA Big prime picking
gb flag

Is the random picking of big n-bits random numbers for primality test a time sensitive operation?

If so, would an heuristic for limiting the search space (about 5-10x) without missing out on any prime be an interesting addition?

Score: 3
Novice_researcher avatar
Indifferentiability of Sponge Construction
br flag

In the case of sponge construction, it is shown to be differentiable from a RO. In the paper by Bertoni et al., what is meant by the node being saturated. How does it become saturated and the condition which leads to error in the simulator was not clear.

Paper link: http://citeseerx.ist.psu.edu/viewdoc/download;jsessionid=09F733C00E75E6BB3E3537ACFAE4396E?doi=10.1.1.544.7974&rep=rep1&type=pd ...

Score: 1
Distribution of elliptic curves with rank 2?
au flag

An elliptic curve defined over a finite field is either cyclic, or a direct sum of two cyclic groups. In cryptography, we use exclusively the former. I was wondering if there is any result on how common (or rare) are rank-2 elliptic curves defined over $\mathbb{F}_{q}$ for a prime power $q$.

(They don't seem rare. For a fixed prime $p$ of 64 bits, I sampled 1000 random curves defined over $\mathbb{F ...

Score: 0
Serzh Nechyporchuk avatar
Can form of elliptic curve digital signature equation be simpler?
cn flag

I am curious why equations for signing/validating with ECDSA have forms they have. Is it possible to use simpler equation that have same properties.

For example, this is an equation I found in the book on Bitcoin:

$$ s = (z + re)/k $$ where,

$r = x\_coordinate\_of(k \cdot G)$,

$e$ - private key,

$z$ - message hash,

$k$ - random number,

$(s, r)$ - signature

What is interesting is that original paper fo ...

Score: 0
Generating private keys based on the list of ciphersuites available
my flag

I am building my own MQTT based network for which I would generate my own ca/server/client certificates for authentication.

The goal here is to keep the message sizes as small as possible so as to reduce the bandwidth traffic, but I already know that the TLS layer adds quite an overhead to the traffic it sends. Namely, with the client certificates, I would actually have to send the client certificate t ...

Score: 2
RIPEMD160 - how were these constants created?
cn flag

I have been through several sources and papers, but I can't seem to find how these rotation constants were created. Are these constants arbitrary, or were there chosen by some kind of permutation? I can't really find any source.

The order of the left rotates on the left hand side are:

{{11, 14, 15, 12, 5, 8, 7, 9, 11, 13, 14, 15, 6, 7, 9, 8}, //Round 1 
{7, 6, 8, 13, 11, 9, 7, 15, 7, 12, 15, 9, 11, 7, ...

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