Cryptography

Modern

RSA

Use RSACtfTool for any RSA keys which appear to be obviously weak. It runs a full suite of tests so it can be used to rule out anything obvious.

./RsaCtfTool.py --publickey ./key.pub --uncipher ./ciphered\_file

Elliptic-Curve Cryptography

When trying to decrypt or encrypt with elliptic-curve cryptography the recommended tool is seccure or python-seccure.

seccure.decrypt(ciphertext, b'my private key')

Classical Ciphers

The most difficult element of cracking a cipher is identifying it's type. There are a number of markers however that can help in reducing the search space. A good resource for this is Practical Cryptography's Guide.

A critical skill in cracking a cipher is identifying the type of cipher it has been encrypted with, then practical cryptography has a good guide to allowing you to begin initial analysis.