Latest Crypto related questions

Score: 2
Post processing method for True Random Number Generator
de flag

I am finding the post-processing method to improve the randomness of the True Random Number Generator. Especially, TRNG can pass the NIST SP 800-22 after applying the post-processing.

I tried to apply the Enocoro-128_v2 Pseudo-Random Number Generator as a post-processing method for TRNG. TRNG will supply the seed for Enocoro. Then, Enocoro works and generates the ouput. After applying this method ...

Score: 0
phantomcraft avatar
Does the security margin of Kalyna block cipher double per for additional 4 rounds? Would be possible to create a version of it with larger key sizes?
pf flag

I believe this question should be directed to the authors of Kalyna block cipher, but I think they cannot answer me because of the war they are facing in their country actually.

I know that AES uses this criteria for adjusting the rounds in accord to different key sizes: [key size]/32+6

Kalyna block cipher has 10 rounds for 128-bits of key size, 14 for 256-bits and 18 for 512-bits. I can see that fo ...

Score: 1
hmngwn avatar
A way to get the public key of a RS256 JWT from its headers and payload?
cn flag

I have a RS256 JWT, I'd like to find out its public key. Because I know the header, payload and I have the encrypted signature, is there a way to obtain the public key that made the signature from these elements?

Score: 2
phantomcraft avatar
What would be the disadvantages of very large block sizes in block ciphers?
pf flag

Let's suppose someone creates a block cipher with 8192-bytes of the block size (65536-bits) or maybe 16384-bytes of the block size (131072-bits).

What would be its disadvantages over a block cipher with smaller block sizes like 128 or 256-bits?

Score: 2
DannyNiu avatar
How important is constant-time verification of lHash label in RSA-OAEP?
vu flag

In my hobbyist project implementation of RSA-OAEP, I omitted support for labels at the beginning. I set the label to empty string on encryption and ignored the label on decryption.

Now I'm adding a special function to set and test the label, but it's not constant-time yet. The security note in PKCS#1v2.2 says that the verification of the label along with other ciphertext verifications should be don ...

Score: 4
Paul Uszak avatar
What is "entropic security"?
cn flag

I've come across a form of cryptographic security that I've never heard of: entropic security. I've read the Russel et al abstract and that doesn't seem to bear much relation to the wiki article.

Things that confuse me are like:-

"Deterministic encryption" :A deterministic encryption scheme (as opposed to a probabilistic encryption scheme) is a cryptosystem which always produces the same cipherte ...

Score: -2
Leli avatar
Let negl1 and negl2 be negligible functions
in flag

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can we still consider the second function negligible ? is there any main differences between them?

Score: 5
forest avatar
Average false-positive rate for a round of Miller–Rabin
vn flag

I'm aware that the Miller–Rabin primality test will claim primality for a composite number with at most a $\frac{1}{4}$ probability for some arbitrary, odd composite $n$ and a random witness $a$ chosen uniformly in the range $[2,n-1)$. What is the actual average chance that that the test falsely claims that the number is prime? How does the chance change as the size of $n$ goes up? How does the chance c ...

Score: 2
Signatures from asymmetric encryption
in flag

Let $(K_{enc},K_{dec})$ be an asymmetric key-pair. It seems to me that a signature scheme can be created by letting the public verification key be $K_{ver}=K_{dec}$ (the asymmetric decryption key) and the secret signing key be $K_{sign}=K_{enc}$ (the asymmetric encryption key). Say with $H$ some hash function and $m$ to be signed: $$ s=\texttt{sign}(m,K_{sign})=\texttt{encrypt}(H(m),K_{enc}) $$  ...

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