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1500 questions
28
votes
1 answer
what is the difference between proofs and arguments of knowledge?
What is the difference between proofs and arguments of knowledge in the context of zero-knowledge?
I have read this sentence in this ePrint:
It is useful to distinguish between zero-knowledge proofs, with
statistical soundness, and zero-knowledge…
MH Samadani
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28
votes
3 answers
Is this password migration strategy secure?
I want to upgrade the security of some existing databases of users' authentication tokens strictly for the purpose of making sure that if the database is stolen, attackers will not be able to guess any but the weakest passwords in a reasonable…
Major Major
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28
votes
2 answers
HMAC vs MAC functions
I've read definitions of MAC and HMAC, but can't say I've completely grasped the differences.
What are principle differences?
When to use one and when the other?(Typical Use Cases)
Matteo
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28
votes
2 answers
Unpredictability of X.509 serial numbers
About X.509 certificates serial numbers the RFC 5280 says:
The serial number MUST be a positive integer assigned by the CA to each certificate. It MUST be unique for each certificate issued by a given CA (i.e., the issuer name and serial number…
Jcs
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28
votes
2 answers
How does a chosen plaintext attack on RSA work?
How can one run a chosen plaintext attack on RSA?
If I can send some plaintexts and get the ciphertexts, how can I find a relation between them which helps me to crack another ciphertext?
user1829
28
votes
2 answers
How were the DES S-box values determined?
It seems like the S-boxes in DES have essentially random values.
How were these chosen?
samoz
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28
votes
1 answer
Multi-party encryption algorithm
To give some foreground information: I acknowledge that I am a cryptography newb and not by any means an expert (and probably never will be).
In a recent CS class we had several assignments writing and implementing RSA and Diffie-Hellman. It was fun…
Niko
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28
votes
2 answers
What is a hard-core predicate?
I read this article on Wikipedia: Hard-core predicate.
Still I don't understand what exactly is a hard-core predicate. Is it possible to put this in simple English terminology, and perhaps with a simple example?
Kai
27
votes
3 answers
Why is the P-521 elliptic curve not in Suite B if AES-256 is?
In the NSA's document, "The Case for Elliptic Curve Cryptography" (archived), we have
+---------------+-------------------------+-----------------+
| Symmetric Key | RSA and Diffie-Hellman | Elliptic Curve |
| Size (bits) | Key Size (bits)…
DeepSpace101
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27
votes
7 answers
Is there any famous protocol that were proven secure but whose proof was wrong and lead to real world attacks?
Are there moderns (post World War II) and famous protocols that were proven secure (in any model: game-based, UC...) but whose proof was wrong and could have led to real-world attacks?
Note that:
I'm not really concerned about attacks on the…
Léo Colisson
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27
votes
2 answers
Is there a hash function which has no collisions?
Is there a hash function which has no collisions?
To clarify: it would be some function which would produce variable-length output, and never produce the same output for differing input. It would also be computationally hard to derive the input from…
benj
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27
votes
1 answer
How does HOTP keep in sync?
My understanding of HOTP is that each password is unique and based on a counter.
$$PASSWORD = HOTP_1(K,C)$$
Where $C$ is an incremental counter.
What I wish to know, is how you keep the client and server in sync? Looking at current systems…
mrwooster
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27
votes
2 answers
How are side-channel attacks executed? What does an attacker need to execute a side channel attack?
I've been reading about side-channel attacks on Wikipedia, and it seems that some of these can only be executed on the victim's computer. (I am specifically asking about the side-channel attacks listed on the Wikipedia page and any more that are…
09182736471890
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27
votes
1 answer
When to use Argon2i vs Argon2d vs Argon2id?
I've read the manual, and multiple articles / StackExchange posts about this topic, but still can't decide which implementation of Argon2 is best for my use case.
I want to securely encrypt passwords in a database in an unshared environment.
After…
J.D.
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27
votes
8 answers
Is there really no use for MD5 anymore?
I read an article about password schemes that makes two seemingly conflicting claims:
MD5 is broken; it’s too slow to use as a general purpose hash; etc
The problem is that MD5 is fast
I know that MD5 should not be used for password hashing, and…
jornane
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