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1 answer

Why are the lower 3 bits of curve25519/ed25519 secret keys cleared during creation?

I am currently experimenting with ed25519 and I noticed that on secret key creation, bit 254 is always set and the lower 3 bits are always cleared. I found that bit 254 is always set to protect against timing attacks in this question: When using…
MepAhoo
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Does Terra Quantum AG break AES and Hash Algorithms?

According to this Bloomberg article: A Swiss Company Says It Found Weakness That Imperils Encryption Terra Quantum AG has a team of about 80 quantum physicists, cryptographers and mathematicians, who are based in Switzerland, Russia, Finland and…
kelalaka
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Why does key generation take an input $1^k$, and how do I represent it in practice?

In my lecture, the lecturer said: Let $K$ be the key generation algorithm. Given a security parameter represented in unary, $1^k$, $K(1^k)$ will output a keypair $(pk; sk)$, known as the public key and the private (or secret) key, respectively.…
juaninf
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"Weaknesses" in SHA-256d?

According to this answer, "SHA-256d" was proposed in one of the Ferguson/Schneier books like so: SHA-256d(x) = SHA-256(SHA-256(x)) Apparently, the motivation for this construction is to avoid length extension attacks. Incidentally, SHA-256d is the…
Nemo
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Low Public Exponent Attack for RSA

I'm having trouble understanding the algorithm for finding the original message $m$, when there is a small public exponent. Here is the example I'm trying to follow (you can also read it in the 'Low exponent RSA paragraph' of this article-…
user1136342
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3 answers

Is Encrypt+HMAC stronger than AEAD?

There are a few posts that I've come across that seem to imply that using regular encryption and a MAC might be better than using the newer AEAD (ie: AES/GCM)…
slipheed
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How effective is quantum computing against elliptic curve cryptography?

I've been reading the Wikipedia page on Elliptic-Curve Cryptography and I came across the following. in August 2015, the NSA announced that it plans to replace Suite B with a new cipher suite due to concerns about quantum computing attacks on ECC.…
Fathima Abdur Rahman
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AES-GCM and its IV/nonce value

I was reading about the differences between the GCM and the CBC modes here and I have a follow up question: In the CBC mode the person who performs the encryption is the one who provides the IV for the encryption -- and the IV is required to decrypt…
user114
26
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4 answers

What makes Quantum Cryptography secure?

This is my current understanding of how Quantum Cryptography works: (The first bit is Quantum Key Distribution) Alice sends a beam of photons to Bob through a quantum channel such as an optical fiber. Each of these photons represent a bit of…
lal lal
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How Far Ahead of Academia Are Government Agencies?

This is a soft question regarding comparisons between government security services (eg, NSA or GCHQ) and open-source research (e.g., academia). Hopefully it's on-topic for this site! In essence, my question is the following. How far ahead (if at…
Sam OT
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Why is it not possible to increase the size of RSA keys indefinitely?

According to this primer on elliptic curves by Ars Technica, when composite numbers get "too" big, they become easier to factorize with Quadratic Sieve and General Number Field Sieve. While this is not explained in detail on the site, it is a common…
fast-reflexes
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What are the odds of collisions for a hash function with 256-bit output?

There are some related questions on the net but I did not understand their solutions. I am reading in a textbook about methods of finding a collision. It states to consider a collision for a hash function with a 256-bit output size and writes if we…
Max
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What tests can I do to ensure my random number generator is working correctly?

In the past I have used the Chi-squared test to check the statistical randomness of my generator. Is this a good test to use? Are there other tests?
this.josh
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Did a certain cryptography method get abandoned due to security flaws in the past?

I am researching how quantum computers affect current encryption methods (RSA and more). However, I remember learning in a course that there used to be a particular encryption method which was popular but suddenly had a very bad vulnerability in the…
Kevin Van Ryckegem
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Which elliptic curves are quantum resistant?

If I want to learn about quantum resistant crytography what are the best resources? Which type of elliptic curves should I be studying?
Imagin Ation
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