# All Questions

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### Generating Polynomials for the MPQS

I'm going to try and eventually factor RSA-100, but my current QS needs a lot of improvement, so I'm going to try and switch over to the MPQS. I'm a bit confused as to how the MPQS works, which is ...
99 views

### Tweaking textbook RSA to make the encryption a Pseudorandom function

Lets say I want to tweak/alter the textbook RSA encryption function to create a pseudorandom function by pre-processing the input. Suppose I do something simple like add 2 to the input before ...
2k views

### Double Encrypting with two different keys

In terms of security, would it be MORE or LESS secure to take, say, an RC4 output (or Serpent) or other, that is encrypted with one key, and to encrypt that output with AES (using a different key)? ...
429 views

### FIPS 140 compliance for encrypted files

Does FIPS 140-2 require specific key sizes, or does it have specific requirements for the data? In other words, if I encrypt a file, how I can check whether it is FIPS-compliant or not? Does only the ...
99 views

### Individual bits of Textbook RSA

This question relates to the underlying RSA assumption. Forgetting about the fact that Textbook RSA is deterministic, I am curious about the assumed strength of the RSA problem. Does RSA hide all ...
3k views

### AES Key Length vs Block Length

This answer points out that certain key and block lengths were a requirement for the AES submissions: The candidate algorithm shall be capable of supporting key-block combinations with sizes of ...
226 views

### Can the encryption exponent e be greater than ϕ(N)?

So I was just wondering in RSA, can the encryption exponent e be greater than ϕ(N)?? For an examples sake, lets just say N = 707, so p = 101 & q = 7. So, we have ϕ(707) = 600. Can I have e = ...
107 views

### use the same pad reversed

Suppose I have a random number (eg 625 467 921). I use it once to encrypt a message OTP style, and when I want to use them again, I reverse them (eg to ...
298 views

### A question regarding relevance of vulnerability of MD5 when linking multiple records together

I have been studying a Supreme Court case "IMS Health vs Sorrel". In this case a Friend of Court brief filled by "Electronic Privacy Information Center" states that use of MD5 hash function to link ...
1k views

### Why is h(m||k) insecure?

Here is the post that explains the failure for doing h(k||m) and I understand it. But I don't understand how h(m||k) is subjected to collison attack, or birthday attack. Please explain?
861 views

### Good enough deterministic PRNG based on hashes

Lets say I have a seed named iv which has a decent amount of entropy. Are there any glaring issues with the following? First 64 bytes are generated by SHA512(iv) Next 64 bytes are generated by ...
3k views

### phi(P*Q) = (P-1) * (Q-1)

I was trying to understand RSA when I encountered the Euler Function. I do understand this: $\phi(P)$, where $P$ is a prime is $P-1$. However it seems that for a number $N$ such at $N=P\cdot Q$ where ...
99 views

### Is there a big RSA Data Set

Is there a big dataset containing RSA public $(n,e)$ and private keys $d$ and primes $p,q$ where $n = p.q$ ?
289 views

### How to generate a random integer in interval $[1, 2^n-1]$ from random integer in interval $[0, 2^n-1]$?

For a project I am working on, I have access to a CSPRNG that outputs a random integer in the interval $[0, 2^n-1]$ for any integer $n$ greater than 0. I cannot use the zero values, so I have my RNG ...
881 views

### Creating a small number from a random octet string

I'm trying to figure out the best way to generate a cryptographically secure random number between 0 and 200 (inclusive) from a cryptographically secure random string of bytes (ie. read from ...
679 views

### security of Felix cipher

I just find this pencil and paper cipher 'Felix' and I want to know how secure it is? EDIT From http://web.archive.org/web/20110825142054/http://topcat.hypermart.net/papers/felix.txt Felix a ...
230 views

### Did Merkle invent cryptographic hashing?

Chapter II of Merkle's 1979 PhD thesis is titled "One Way Hash Functions." The chapter appears to be the first reference to cryptographic hashing. The chapter has no references. Is there an earlier ...
195 views

288 views

### Information leakage in real-time voice encryption

I saw some time ago a post discussing the issues surrounding encryption of speech/voice in VoIP and how it can leak information (can't find it now). Can someone provide an insight into some of the ...
444 views

### Are really, really long passwords any securer than short ones?

Just for fun, I want to encrypt a message that will take about 10 or so years to decrypt. My idea is to encrypt a message with AES-512 with a password one million decimal digits long. Knowing not ...
790 views

### Public key cryptography - public key encrypts and cannot decrypt?

I understand the basics behind public key cryptography, in that each party has two keys - the public one encrypts, and the private one decrypts. What I cannot figure out is, How does the public key ...
I did a CRT challenge yesterday and theres one problem I was unable to solve, probably due to my lack of understanding advanced crypto math. Its about RSA. There are ten given pairs of N and E ...