Latest Crypto related questions

Score: 1
Is there any known/standard encoding or cipher method that uses a 64-character alphabet from byte 30 (ASCII `0`) to byte 6F (ASCII `o`)?
cn flag

Is there any known/standard encoding or cipher method that uses a 64-character alphabet from byte 30 (ASCII 0) to byte 6F (ASCII o)?

I'm trying to reverse-engineer a file format, and I have good idea of what some of the contents of the files should contain, but I'm not seeing any obvious patterns in the data that correspond to my expectations. The biggest peculiarity that I've been able to identify i ...

Score: 0
Apache Server 2.4.53 with Custom Built OpenSSL
in flag

I am trying to launch an Apache server on Ubuntu 20.04 running a custom built OpenSSL, but I don't want to install it on my machine, instead, I want to show the server where it can find all libraries and configuration files relevant to OpenSSL. As you guess, this is an experimental study, so I don't want to mess with my default OpenSSL.

I used the following command to configure my server:

./configure -- ...

Score: 1
dlfls avatar
In RSA, What does gcd(e,phi) != 1 means? Why always choose e = 2^n +1 not 2^n?
in flag

Recently I have few experiences with Questions in RSA which e is 2^n instead of 2^n+1, and that leads to gcd(e, phi) is not equal to 1... Won't this make the private key impossible to get? Is the Rabin cryptosystem the only way out?

Score: 1
Konstantina Mil avatar
How to calculate entropy of a specific cryptosystem?
sa flag

I want to calculate the entropy of a specific cryptosystem such as the Caesar cipher or Vernam cryptosystem etc but I don't quite understand how to do so. Any help?

Score: 2
Rein Ernst avatar
Is it possible to calculate the modular inverse of a secp256k1 public key?
jp flag

I know that it wouldn't be possible to use the extended Euclidean algorithm, since it would require the ability to divide a public key and calculate the remainder. I was wondering if there were any other ways of calculating the modular multiplicative inverse of a point on an elliptic curve (like secp256k1)? Or perhaps a reason why it is provably impossible? Is there a way (other than brute force) to fin ...

Score: 0
Dylk58 avatar
Short description of encryption methods?
jp flag

I can't seem to wrap my head around these encryption methods. I can't find a brief description for any of them.

  • Hash then encrypt
  • MAC then encrypt
  • Encrypt and MAC
  • Encrypt then MAC
Score: 0
Signing a hash of file vs signing a file
uz flag

If person A generated a hash (e.g sha256) of a file and then signed the hash using a private key.

Given person B only has the public key, file, signature and the hash, would verifying the signature using the public key be sufficient to prove person A signed the actual file?

What hashes and algorithms are best suited to this?

Score: 0
Facundo Fleitas avatar
How to reduce Diffie Hellman problem to ElGamal?
ru flag

enter image description here

I'm trying to answer without success questions (ii - iv)

Any hint will be appreciated :)

Score: 0
JamesTheAwesomeDude avatar
Detecting MD5sum collision vulnerability?
cn flag

It's my understanding that MD5 is still resistant to preimage attacks in the general case, but that an attacker may still launch a second preimage attack if an innocent file is "unlucky" enough to be a viable collision candidate.

  • What are the odds of a uniformly random file of length $512n$ bits being a candidate for an MD5 collision attack?
  • Is it possible to detect current state-of-the-art attack ...
Score: 0
dlfls avatar
RSA question for public exponent is an even number but not 2, and not big
in flag

While Public exponent is an even number which means Can't get the d in normal way since gcd(e, phi) won't be 1, and in this case only used one prime number for N (multiple uses for one prime number) What is the idea of getting the m,could p = 3 mod 4 be helpful? Thank you for any idea.

Score: 0
Tools to debug handshake failure after client key exchange, change cipher spec and encrypted handshake message TLS1.2
pk flag

Hello I have been receiving Description : Handshake failure after sending client encrypted handshake message to the server. Is there any tools I can use instead of wireshark to detect the source of this problem because wireshark did not really help me at this point. wireshark_capture

Score: 2
brethvoice avatar
Hotbits vs. Random.org vs. Anything else?
jp flag

I was searching for a random seed to use with a pseudo-random number generator (not trying to encrypt anything). I went to the following web sites:

https://www.fourmilab.ch/hotbits/secure_generate.html

https://www.random.org/

It appears that Random.org has a solid history and is not experiencing problems with DDoS attacks because they do not require an API key. I obviously would not want to use anything  ...

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