# All Questions

1answer
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### Some terms related to secret sharing: Optimality, What does it mean?

In any secret sharing scheme we have to develop step by step. After constructing such scheme we need to reduce share size. Why? e.g. Robust secret sharing scheme is modified Shamir secret sharing ...
0answers
37 views

### Is the ring learning with errors problem still hard if the errors are drawn from some subspace?

Let $R=\mathbb{Z}_p[x]/x^n+1$ be the ring used in normal RLWE, which is linear space over $\mathbb{Z}_p$ with dimension of $n$, let $S$ be a linear subspace of $R$ which described by linear ...
0answers
56 views

### Name of an archaic type of RSA padding (0BBBBBBB…)

In some legacy code, I encountered RSA signature padding in the following format (hexadecimal): 0B BB BB BB BB BB BB ... BB BB <hash> Is there a name for ...
1answer
64 views

### Why is Diffie-Hellman used instead of just RSA in key-exchange (TLS, IKE)?

Why should a key exchange protocol (such as in TLS or IKE) use Diffie Hellman? Why not just use RSA? For example: Alice picks a random session key, signs it, encrypts it with Bob's public key, and ...
0answers
42 views

### How can I obtain the raw decimal value of an RSA key's modulus?

So maybe I'm thinking about this too hard, or maybe I'm missing a piece of information. We'll use Google for this example. Say I wanted to obtain the modulus of Google's current public key. Well I ...
3answers
626 views

### Advantages/disadvantages of using symmetric encryption function as hash function?

Next to the traditional MD5 and SHA-1, other hashing algorithms exist based on symmetric encryption algorithms. An example is the Matyas–Meyer–Oseas construction. What are the advantages/...
2answers
41 views

### Why is synthetic IV (SIV) mode considered deterministic authenticated encryption (DAE)?

I was just going over my (old) notes from Coursera's Cryptography I course, and I was puzzled by the description of SIV as providing deterministic authenticated encryption (DAE). The general SIV ...
1answer
56 views

### identifying presence of encryption of zero in additive homomorphic encryption

Lets say the server has corpus of ciphertext contains $enc(a),enc(b),enc(c), \dotsc enc(x)$. The encryption function is an additive homomorphic scheme (like Paillier). The server knows only the public ...
1answer
81 views

### Calculating Polynomial Inverse with extended euclid in java

I'm trying to understand the NTRU-PKCS and therefor I wanted to code a naive Version of it. Now my Problem: I tried to calculate the inverse of a Polynomial with an extended Version of euclids ...
1answer
67 views

### Using Pollard's lambda in a key-recovery attack on DH

I've become interested in writing an exploit for the OpenSSL vulnerability here (CVE-2016-0701). Running through the bullets describing the attack, I can follow up to the last bullet point. Reviewing ...
0answers
11 views

### Can you extract the encryption key of a computer with full disk encryption via malware? [migrated]

I recently discovered the subject of cold boot attacks which are able to extract the encryption key of the ram memory after the computer has shut down. and from what I understand is that law ...
0answers
30 views

1answer
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### How hard is it to generate a simultaneous MD5 and SHA1 collision?

I was recently reading that MD5 is "broken" because it's pretty easy to generate collisions (like 2^(L/2)). And the SHA1 (theoretically) fares no better. The ...
0answers
38 views

### Countering Cryptographic Attacks

By reading Camellia Design and Analysis document following is my understanding about few cryptographic attacks from designer point of view. Differential and Linear Crypt-analysis. Number of Active ...
1answer
34 views

### How does the key size in supersingular isogeny schemes relate to their security level?

I'm looking at the De Feo, Jao, and Plût 2014 paper: Towards quantum-resistant cryptosystems from supersingular elliptic curve isogenies. My understanding of section 3.2 Key Exchange, is that Alice'...
2answers
34 views

### What are KDF parameters in OpenSSL command-line utility for enc?

I refer to https://www.openssl.org/docs/manmaster/apps/enc.html and see that the only parameter for key derivation which I can set explicitly (not considering the obvious ...
0answers
84 views

### How to generate 1000 prime number of 1024-bit with much less time?

I am generating thousand prime number of 1024 bit each. But it takes lots of time. My procedure is as follows. Generate prime number using ...
2answers
55 views

### AES encryption for pairwise identifiers

I'd like to map a random ID of 16 bytes (sourceID) to another random ID of 16 bytes (targetID). The operation should: only be reversible by me be deterministic There are about 1 million source ...

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