Cryptography Stack Exchange
Cryptography Stack Exchange

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1500 questions
59
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2 answers

Is the software that uses PGP broken, or is it PGP itself?

PGP is all over the news (even on TV) and there seems to be a lot of confusion about it. For the time being, people face articles like Attention PGP users: new vulnerabilities require you to take action now which tell readers to deactivate their PGP…
Mike Edward Moras
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58
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5 answers

What are the chances that AES-256 encryption is cracked?

I'm currently building a web application and would like to encrypt all data on the back-end. I was thinking of using the AES-256 encryption but wasn't sure how safe it was. I did that math and felt safe. I took this model to a professor at my…
Jacob Henning
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57
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3 answers

Do these new insights into prime numbers affect encryption security?

Quanta Magazine reports: Two mathematicians have uncovered a simple, previously unnoticed property of prime numbers [...]. Prime numbers, it seems, have decided preferences about the final digits of the primes that immediately follow them. Among…
user
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57
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2 answers

ECDSA vs ECIES vs ECDH

Recently I started studying Elliptic Curve Cryptography and I just loved it. I want to transfer some big data (like 3KB), What is the best method, ECDSA, ECIES, or ECDH (and why)? I am confused, how should I choose between ECDSA, ECIES and ECDH?
user3160055
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56
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6 answers

Kerckhoffs’ principles – Why should I make my cipher public?

As I understand it, the less people know about the internals of my protocol or cipher, the more secure the protocol is. However Kerckhoffs's principle states that A cryptosystem should be secure even if everything about the system, except the key,…
rath
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56
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11 answers

How do hashes really ensure uniqueness?

This might seem an impractical and unnecessary conversation, but I feel it's something I need to clarify. Especially, as I just got my first developer job in a blockchain startup. So hashes are said to generate the same thing for any information it…
James Kumar
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56
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7 answers

One Encryption, Many Decryption Keys

I would like to share access to encrypted data among many recipients. I do not know the recipients ahead of time (when encrypting the data). Once the data is encrypted, I do not have access to the plaintext (so I cannot re-encrypt). Right now, I…
Justin Bailey
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55
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2 answers

What security authorities and standards reject $e=3$ in RSA, when, and with what rationale?

 In RSA, some security authorities and/or standards allow the public exponent $e=3$, others require or recommend $e>2^{16}$ (or perhaps some other minimum). I gathered the following: PKCS#1 allows $e=3$ for both RSA digital signature and encryption…
fgrieu
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55
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3 answers

Why is public-key encryption so much less efficient than secret-key encryption?

I'm currently reading Cryptography Engineering. After giving a high level explanation of the difference between secret-key encryption and public-key encryption, the book says: So why do we bother with secret-key encryption if public-key encryption…
user670
55
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2 answers

Timing attack and good coding practices

How would timing attack occur on a particular code but not in another code (because of good coding practice)? Could anyone give an example? I am having trouble figuring out how timing attacks would occur based on the way the code is written.
asdfasd
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54
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2 answers

Why use an Initialization Vector (IV)?

Why use an Initialization Vector (IV)? How are IV's used? What are the advantages/disadvantages of using an IV? Why use an IV instead of a longer key in which some section of the key is public? What happens to various security properties if an IV…
Ethan Heilman
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54
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10 answers

Now that quantum computers have been out for a while, has RSA been cracked?

D-wave systems has released a commercially viable quantum computer. This means in theory, that all asymmetric encryption algorithms — such as RSA — are now useless due to the speed at which quantum computers can factor. Has RSA been cracked yet? If…
bbosak
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54
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1 answer

Password hashing security of argon2 versus bcrypt/PBKDF2?

I wonder if it can be approximated how much of a security margin the new argon2 hash, winner of the password hashing competition, can give over bcrypt or PBKDF2, for an attacker using large GPU systems. Practically speaking, if I have had a…
azren
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53
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1 answer

Why do 5G, 4G, etc., use non-conventional algorithms?

Looking up information about 5G and the previous 3GPP standards, why have they been incorporating non-conventional algorithms into the standards? For example, AES has been considered secure for ages and there is lots of support for hardware…
MCCCS
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53
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2 answers

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 ECDSA, would this require less space with the same…
Maestro
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