# All Questions

1answer
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### textbook RSA signature scheme security

Are textbook RSA signatures secure if an Adversary does not have access to ask signing oracle queries?
3answers
108 views

### Three party coin flipping protocol with only 2 active participants

Is there a coin flipping protocol where: Alice, Bob and Carol don't trust each other, and The coin is flipped only by Alice and Bob, and The result must be trusted by all three participants.
2answers
111 views

2answers
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### Has there been any cryptanalysis of AES under a non-uniformly distributed key?

The standard security property demanded of a blockcipher is that it be a pseudo-random permutation; i.e., given a uniformly random key, the blockcipher should be computationally indistinguishable from ...
1answer
174 views

### Is this modified Schnorr signature scheme secure?

Signing Let y = g^x, which is your public/private keypair. Let r = g^v, for random v Let c = H(M) Let z = (v + cx) mod q The signature is the pair (r,z) Verifying g^z = ry^c mod p We further ...
1answer
239 views

1answer
186 views

### Can Bitcoin HD public keys be used for symmetric encryption?

I asked this at bitcoin.stackexchange.com first, but it seems that this is more of a crypto-question anyway. I'm interested in using a Hierarchical Deterministic Bitcoin wallet branch as a "shared ...
1answer
476 views

### Interleaving bytes to make an effectively larger block size

Will applying a 16 byte bit block cipher such as AES over a 256 byte block to in the following way result in a much stronger cipher:- Apply block cipher with first key digest to each 16 byte group. ...
1answer
379 views

### Revealing random bit permutation

I am new in cryptography. I want to determine the complexity of revealing a random bit permutation which is used as block cipher for plaintexts (bitstrings of length n). An adversary catches different ...
2answers
264 views

### OCB nonce usage

I've just come across this piece of code in Bouncy Castle's implementation of OCB Mode: ...
2answers
827 views

### Can I crack an AES string if I have all these parameters?

This is for a challenge at followthewhiterabbit.trustpilot.com: Knowns: The algorithm is AES (Rijndael) Blocksize: 128 Keysize: 256 You only need to find the first 6 bytes of the ...
1answer
625 views

### generate hash of all handshake messages for verify data (DTLS)

I am trying to create a DTLS client finished packet, where I need to generate verify data for handshake hash is need. And here I want to know how to generate handshake hash. As of now I am doing like ...
1answer
183 views

### Is it possible to get better randomness by using multiple PRNGs?

I don't know if this question even makes sense, but: Is there be any benefit or impact to some sort of hierarchical (e.g. a PRNG drives the decision for which PRN to pull from a set of PRNGs) or ...
3answers
269 views

### Encrypt-then-MAC: full random keys or keys derived from master key?

I have this scenario where I use Encrypt-then-MAC (AES256-CBC and HMAC-SHA256) with keys generated by a CSPRNG (specifically, SecureRandom in Java). I'd like to know which is better: Use the CSPRNG ...
1answer
198 views

### Does this protocol provide Perfect Forward Secrecy / are there potential security flaws?

We have a HMAC key (128 bit/16 bytes) an AES key (128 bit/16 bytes) an AES IV (128 bit/16 bytes) a random salt (128 bit/16 bytes) Each packet is signed with a HMAC (SHA256) After each packet is ...
1answer
316 views

### Is AES-256 over AES-128 weakening the original encryption?

When transfering data using TLS the browser and server agree the cipher suite to be used - so for example this could be chosen as AES-128 and is (probably) outside of my control. If I separately ...
1answer
113 views

### RSA private exponent primality

I know that the public exponent is always a prime, but what about the private exponent? Is it always a prime too?
2answers
285 views

### Point addition and doubling in Ed25519 (ref10)?

I just migrated CodesInChaos' C# port of Ed25519(ref10) to Java, and everything works fine. (I.e. I get the same results for key generation, signature and verification.) Now, I would like to do a ...

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