# All Questions

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### Request for 1024-bit primes $p$ , subgroup $q$ and subgroup generator $g$

I need to find a prime $p$ of $1024$ bits with a $160$ bit sub group size $q$, such that $q|p-1$ , and $g$ is the generator of the sub group size $q$. I'm looking for the numeric values of $p$ , $q$ ...
109 views

### Secure way to compare two secret numbers without disclosing them?

For example, two people want to know who is the older, without disclosing their age. Is there a secure way to do this without a third party involved?
172 views

### AES implementation in java that allows key of 320-bit length [closed]

I need an implementation of AES(Rijndael) in java that allows use of a 320-bit key. Please suggest a reliable implementation
349 views

### Hashing a password with SHA256 on the client then bcrypt on the server

I'm trying to implement a cryptographically secured storage site (not Mega, or anything similar) and am trying to prevent the user's password from ever touching the server. The password is used to ...
152 views

### What is 'security margin'?

I have been academic papers about Rijndael, Serpent, and Twofish, and there is this term that is vague to me. I cannot find a tangible definition in google. Can someone briefly define, describe, ...
102 views

### Obtaining a key that's using ice algorithm

I have a text file that has been processed by the SNOW steganography tool that uses ICE encryption. However, I do not know the key that would enable me to decrypt and retrieve the message hidden. ...
618 views

### AES-CTR vulnerability to cryptographic oracle

I am new to cryptographic issues and from what I googled so far I could not retrieve the information I need. Consider the use of AES-128 in CTR mode. Let M be the set of possible plaintexts, for ...
95 views

### Tell me about non-MD5/SHA1 key fingerprints

I understand there are specifications for public-key fingerprints that use modern hash algorithms like SHA2. What are they?
400 views

### RSA primes vs. largest known primes

In the context of a new largest (mersenne) prime number being found this week - The largest known prime number is now 2^57,885,161 − 1, and it took 5 years to find ...
192 views

### What are alternatives to the random oracle model for modelling hash functions? [closed]

I was looking for more realistic alternatives to the ROM for describing hash functions in theoretical proofs. I came across the common reference string model (where hash functions can be modeled as ...
351 views

### Bitcoin, couldn't a miner steal money? [closed]

What prevents a miner's block from being accepted across the network if the hash checks out when miner forges transactions in the block? For example, lets say I'm mining and I want to steal money ...
162 views

### Is such a crypto-system available?

$E(k_1, pt) = c_1, E(k_2, c_1) = c_2, D(k_{new}, c_2) = pt$, where $k_{new} = f(k_1, k_2).$ Sharing $k_{new}$ and $k_2$ should reveal no information about $k_1$. Clarifications: Being able to ...
693 views

### How to check the strength of an encryption algorithm?

I asking for advice on how to check strength of an encryption algorithm.
92 views

### What is RSA key normalization?

How can I understand the term RSA key normalization? What exactly is done in the process?? Please explain.
400 views

### Why does the recommended key size between symmetric and assymetric encryption differ greatly?

In various articles it is mentioned that for secure communications, the recommended key sizes are 128-bit key size for symmetric encryption (which makes it $2^{128}$ possible keys?) and 2048-bit key ...
62 views

How does padding in PMAC work? I have been told two stories: Firstly, I have been told that it works similar to CMAC padding, and secondly, I have been told that it does not need padding. I find the ...
209 views

### Source for examples with broken cryptography

I've heard again and again that many crypto systems have been broken in the past for one reason or another and that it is best to use one that has been peer reviewed, etc etc. However, I've yet to see ...
154 views

### Is there a problem with constructing a CSPRNG using MD5 or SHA1?

Is there any security concerns with building a CSPRNG using a broken hash function like MD5 or SHA1? The design is such that a CRC-like function is used for mixing entropy and MD5 is used as the ...
226 views

### What are some approaches to attack an triple key polyalphabetic cipher when the IV key and PT key are known?

The cipher is an triple key polyalphabetic cipher also known as an Quagmire IV by the ACA. An example would be here: Quagmire IV example and info (pardon the ads) I posses the IV key and the PT key. ...
208 views

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### Questions on rank-attacks in Multivariate Cryptography

While reading this article on rank attacks on STS (a public-key scheme based on Multivariate Quadratic (MQ) equations), I stumbled upon some claims that I've also seen in other presentations on ...
42 views

### School exercise on untrusted channel comunication [duplicate]

Possible Duplicate: Why is H(k||x) not a secure MAC construction? I've the following problem: two parties, A and B, share a secret key Kab. M is a plaintext message, H an unkeyed hash ...
211 views

### RSA and One Time Password (OTP) service

What is the expert cryptographic opinion on the following? Assume that there is a web server and a client on web page. User on the Client calls an OTP web service on the server which: creates a RSA ...