Cryptography Stack Exchange
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2 answers

How does one verify a GPG/PGP key revocation?

After revoking a key and sending the revocation to MIT's keyserver, I noticed that the key is listed as such: pub 2048R/XXXXXXXX 2011-01-01 *** KEY REVOKED *** [not verified] Who is responsible for the 'verification of the revocation'? Does the…
earthmeLon
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How do I apply differential cryptanalysis to a block cipher?

I have read a lot of summaries of block ciphers particularly with regards to the NIST competitions stating that reduced-round block ciphers are – for example – vulnerable to differential cryptanalysis. I have a general idea that the application of…
user46
31
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2 answers

What is a white-box implementation of a cryptographic algorithm?

What is a white-box implementation? Does a white-box implementation have specific properties?
ir01
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Why are primes important for encryption

Why are primes so important? Why can't we just use a random number? My guess is that it's because finding a random prime require more computing power, than finding a random number. Can anybody confirm this?
KaareZ
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Is HMAC-DRBG or Hash-DRBG stronger?

Out of the two deterministic random bit generators defined in section 10.1 of NIST SP 800-90A (i.e. based on hash functions), which one is cryptographically stronger? Hash-DRBG (Section 10.1.1) HMAC-DRBG (Section 10.1.2) Is there any other…
Lunar Mushrooms
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3 answers

Is it possible to derive the encryption method from encrypted text?

Is it possible to identify the encryption method, or at least rule out some of them, by looking at the encrypted text? For example, if you have 3 encrypted strings where the first 10 characters are the same on each of the strings.
Shiraz Bhaiji
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31
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2 answers

When using Curve25519, why does the private key always have a fixed bit at 2^254?

When using Curve25519, the private key always seems to have a fixed bit set at position $2^{254}$. Why is that? Is there any good reason to use a fixed positioned most-significant-bit in the private key?
Trina
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9 answers

RSA with small exponents?

Just to establish notation with respect to the RSA protocol, let $n = pq$ be the product of two large primes and let $e$ and $d$ be the public and private exponents, respectively ($e$ is the inverse of $d \bmod \varphi(n)$). Given a plaintext…
Elliott
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Why is FIPS 140-2 compliance controversial?

I was reading the comments of an article about a proposed new implementation of /dev/random in Linux today, and someone remarked that it must be bothersome to go through 43 revisions and still not have your patch landed. A few comments down the line…
Newbyte
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Assuming a 1024qb quantum computer, how long to brute force 1024bit RSA, 256bit AES and 512bit SHA512

Assuming in the future there was a functioning 1024 qubit quantum supercomputer and it could run Shor's algorithm or Grover's algorithm to crack encryption very quickly. I'm interested in how the number of qubits translates to performance…
user7827
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How was this 2048 bit number factored so fast?

I'm working on a CTF. The challenge is to get the contents of an encrypted message given the ciphertext and the 2048-bit RSA public key. I did finally get the flag after a few hours, but I'm still not sure why the first step worked. The first step…
rainbowkitty227
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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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Why is asymmetric cryptography bad for huge data?

I've been told that asymmetric cryptography requires that the message to be encrypted be smaller than its key length. Why is this? I know about hybrid encryption, which uses symmetric encryption to resolve this problem. But I still want to know why…
K_X
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8 answers

Can you use memory errors as a source of randomness for cryptography?

Obviously, if you need a random number for cryptography, your code should use an api that gets it from hardware. However, not all hardware has a SRNG available. If you are working on a security critical application, and hardware RNG is not available…
TheCatWhisperer
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Rubik's Cube as Encryption

Consider this scenario: Alice gets a Rubik's Cube and peels off the colors from each piece. She then writes a small message on one of the faces of the cube and fills the remaining pieces with random letters. Then, she scrambles the pieces in a way…
yasar
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