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waves over lambda
Published: April 2, 2026
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Useful tools for Cryptography
- ROT / Caesar CipherDecode Caesar-shifted and ROT-encoded text. Drag the shift slider or scan all 26 rotations at once.
- Affine CipherEncrypt, decrypt, or brute-force affine ciphers using E(x) = (ax + b) mod 26. Brute force ranks all 312 key pairs by English letter frequency.
- XOR CipherXOR-decrypt hex or text ciphertext with a known key, or brute-force the single-byte key automatically.
- Vigenère CipherEncrypt or decrypt text with the Vigenère polyalphabetic substitution cipher using a keyword.
Related reading
- RSA Attacks for CTF CryptographyA complete guide to RSA attack techniques that appear in CTF competitions: small public exponent, weak modulus factoring, common modulus, Wiener's attack, and RSA oracle decryption - with picoCTF challenge links throughout.
- Base64, Hex, and Common CTF Encodings ExplainedIdentify and decode every encoding you will encounter in CTF competitions: Base64, hex, binary, octal, ROT13, URL encoding, Morse code, and more -- with one-liners for each.
What to try next
- CryptographyMedium
Black Cobra Pepper
A custom cipher reminiscent of AES. Reverse engineer the S-box and cipher operations to decrypt the flag.
- CryptographyMedium
ClusterRSA
RSA with more than two prime factors. Factor N using a multi-prime factorization tool, then compute phi and decrypt.
- CryptographyMedium
cryptomaze
A flag encrypted using LFSR-derived AES key. Recover the 128-bit LFSR key sequence, build the AES key, and decrypt the flag in ECB mode.
- CryptographyMedium
Not TRUe
A lattice-based cryptosystem. Use a lattice attack to compute the private key from the public information and decrypt the flag.
- CryptographyMedium
Related Messages
Two RSA encryptions of related messages (same key, minor difference). Apply the Franklin-Reiter related-message attack to recover the flag.