Cryptography Stack Exchange Community Digest

Top new questions this week:

Do certificates need to be stored as encrypted?

The titles says most of what we're confused with. Here's some details: On an embedded device, we have a microcontroller and external flash memory. This memory can be easily read and written to in ...

public-key certificates  
asked by Ashley Duncan 5 votes
answered by poncho 16 votes

What does that mean, that A5/1 is clocked?

What does that mean, that A5/1 is clocked? What happens if the clocking bit agrees with the majority bit?

stream-cipher lfsr  
asked by Tom 4 votes
answered by kelalaka 4 votes

NIST LWC finalists (AEAD) vs ChaCha20-Poly1305

NIST LWC finalists announced. My question is that how finalists are faster or slower than current golden lightweight AEAD standard -- ChaCha20-Poly1305. Some benchmark among chacha20-poly1305 vs LWC ...

chacha lightweight  
asked by jannik 3 votes
answered by Raoul722 3 votes

Are newer crypto currencies intrinsically more energy efficient, or just newer?

There's a lot in the news about the energy cost of Bitcoin recently. Recently Elon Musk talked about "currencies using <1% the energy per transaction of BTC". This page provides some ...

asked by Mr. Boy 3 votes

Public signature of challenges as authentication

Assuming you trust a client's public signature keys, a simple authentication protocol would be to send a long random string challenge, and get the client to sign it Since most of authentication still ...

asked by lurscher 2 votes
answered by Gilles 'SO- stop being evil' 2 votes

What does a linear function with huge order mean?

I am reading this paper "Farfalle: parallel permutation-based cryptography", and there are some terms that I do not understand. Page 4 says ratio efficiency vs. safety margin. What does ...

asked by juaninf 2 votes
answered by kodlu 1 vote

Efficient peer to peer untrusted signature aggregation

Suppose I had a peer to peer system, there are a few writers with the same signing key, and all readers have the verification key. A naive system is that each document $d_1..d_n$ gets signed $s_i=sign(...

asked by user1138184 2 votes

Greatest hits from previous weeks:

Why haven't any SHA-256 collisions been found yet?

I've been thinking about this for a few days, a SHA-256 algorithm outputs 64 characters which can either be a lowercase letter or a number from 0-9. Which should mean that there are 64^36 distinct SHA-...

collision-resistance sha-256  
asked by ninesalt 70 votes

How are the AES S-Boxes calculated?

I'm trying to understand how the AES S-Boxes are calculated. I understand how the multiplicative inverse is calculated over $GF(2^8)$, but I'm confused by the description of the affine transformation. ...

aes s-boxes  
asked by ConditionRacer 15 votes
answered by Richie Frame 16 votes

How does RSA signature verification work?

I understand how the RSA algorithm works for encryption and decryption purposes but I don't get how signing is done. Here's what I (think) I know and is common practice: If I have a message that I ...

rsa signature  
asked by Krumelur 78 votes
answered by poncho 89 votes

Cipher Feedback Mode

I can't understand what CFB really is. It said in Wikipedia that CFB is same as CBC, but I find that CFB is more difficult than CBC. Can someone explain to me how CFB works. Such as how ...

encryption aes modes-of-operation cfb  
asked by goldroger 9 votes
answered by poncho 12 votes

Is Caesar cipher perfectly secret?

The only time a shift cipher considers to be perfectly secure is when used on a single letter of plaintext and no more. Having that in mind, we can say it is certainly not perfectly secure. Caesar ...

encryption symmetric  
asked by whitehat.c 6 votes

Signatures: RSA compared to ECDSA

I'm signing very small messages using RSA, and the signature and public key are added to every message, which requires a lot of space compared to the actual content. I'm considering switching to ...

rsa signature authentication dsa  
asked by Muis 48 votes
answered by poncho 43 votes

Second pre-image resistance vs Collision resistance

From Wikipedia: Second pre-image resistance Given an input $m_1$ it should be difficult to find another input $m_2$ such that $m_1$ ≠ $m_2$ and $\operatorname{hash}(m_1) = \operatorname{hash}...

hash collision-resistance 2nd-preimage-resistance  
asked by ritch 38 votes
answered by yyyyyyy 60 votes

Can you answer these questions?

Lightweight encrypting for BLE advertising packets

I'm new to encryption and this is my first time working with it. I'm currently working on a home project which consists of the equipment in my garage to be attached with a BLE device which sends ...

sha-3 lightweight blake2  
asked by nbafanatic 1 vote

Palisade: EvalMult between plaintext and ciphertext resulting in tower size mismatch

I hope someone can help me understand an error I get when using Palisades. I want to only use the first 329 slots of a BGV ciphertext, and zero out the rest (which at some point contains some '...

asked by Håvard Raddum 1 vote

Is it possible to apply the El Gamal encryption/decryption technique using Edwards curve in Montgomery form

I've been trying to understand the ElGamal encryption/decryption technique. I plan to use it for sending a private message to the server. That is: Alice needs to send $Pm$ (private message encoded via ...

elliptic-curves elgamal-encryption ed25519 montgomery-multiplication  
asked by Bosco Rohan Jacinto 1 vote
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