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1500 questions
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
3 answers
Why does BitLocker not use RSA?
If understand correctly from this post and the Wikipedia page for BitLocker and TPM, by default, BitLocker uses symmetric cryptography like AES. However, TPM is capable of performing RSA encryption.
Given that the RSA key is stored in the TPM, why…
user3862410
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27
votes
1 answer
Is openssl rand command cryptographically secure?
I'm wondering if the openssl rand command produces cryptographically secure random bytes. For example when in need for a random password or token:
openssl rand -hex 32
The man page unfortunately does neither state it's cryptographically secure, nor…
firefexx
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27
votes
2 answers
Why did TLS 1.3 prohibit PGP authentication?
There is a specification, in Informational(!) RFC 6091, for using PGP keys in TLS authentication, although I don’t think it has ever been implemented outside of GnuTLS (it’s certainly not in OpenSSL).
Yet the TLS 1.3 RFC 8446 §4.4.2 goes as far as…
Alex Shpilkin
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27
votes
2 answers
Is there any difference between cryptography and cryptology?
Is there a difference between cryptography and cryptology, if any?
An internet search suggests that both terms can be used interchangeably.
Nathan Aw
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27
votes
1 answer
Why hashing twice?
I'm trying to understand the Bitcoin protocol, and sometimes see instructions like this:
The TransactionId is defined by SHA256(SHA256(txbytes))
or
The hash of the public key is generated by performing a SHA256 hash on the public key, and then…
Timur Lemeshko
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27
votes
5 answers
Timing-Safety in JVM-Languages
How is it possible to write timing-safe code in JVM-languages (Java, Scala, Clojure...)?
Is it possible to make libraries like BouncyCastle safe against timing-attacks?
I know that even in C it is very hard to get those things right – and in C you…
K. Biermann
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27
votes
2 answers
Purpose of DES parity bits
DES has a 64-bit key size, but only 56 of those are used during encryption. The other 8 are "parity bits".
What was the intended purpose of the party bits, and why are they no longer used in modern ciphers?
user9070
27
votes
2 answers
Why is PuTTYgen-created RSA public exponent(e) not in {3,17,65537}?
As far as I know, RSA public exponent(e) should be one of {3,17,65537}.
However, I found PuTTYgen-created RSA public exponent(e) is 0x25(37) by default,as follows, (PuTTYgen version: 0.66)
I am curious why PuTTY uses 0x25(37) instead of…
Matt Elson
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27
votes
2 answers
How to solve MixColumns
I can't really understand MixColumns in the Advanced Encryption Standard, can anyone help me how to do this?
I found some topics on the internet about MixColumns, but I still have a lot of questions to ask.
Ex.
$$
\begin{bmatrix}
\mathtt{d4}…
goldroger
- 1,737
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27
votes
3 answers
Information leakage from the ecryptfs filesystem
I'm wondering what information might be leaked from the ecryptfs filesystem. This is what Ubuntu uses if you check the box for "encrypted home directory" when using the desktop installer, so is probably quite widely used. Key characteristics of…
Hamish Downer
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27
votes
2 answers
When to use RSA and when ElGamal asymmetric encryption
If i am not wrong in cryptography there are 2 basic cryptographic schemes for public key cryptography. RSA encryption whose security is based on the infeasibility of solving the factoring of big primes problem and the ElGamal encryption which is as…
curious
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27
votes
2 answers
Is RSA encryption with a private key the same as signature generation?
It is often said that RSA encryption of a cryptographic hash with a private key is the same as signing (signature generation). And that verification consists of decryption using a public key.
Is RSA encryption with a private key over a cryptographic…
Maarten Bodewes
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27
votes
1 answer
Use cases for CMAC vs. HMAC?
Both can be used to verify the integrity of a message. Assuming you have the needed primitives available to you (i.e. the code space of needing both a cipher and a hash function isn't prohibitive), is there any reason to prefer one over an other? In…
Alex Gaynor
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27
votes
1 answer
Zero knowledge proof protocol example?
Alice is color blind. She never knows if her gloves are matched. Her
brother Bob always teases her saying her gloves are mismatched and
she should go change them. Alice wants to know if Bob is telling the
truth about her…
user10956
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