Advanced Cryptography
Beyond classical ciphers, modern crypto breaks because of how it is implemented, not the math itself. You will factor RSA moduli with Pollard's p-1 and shared-prime GCDs, mount differential power-analysis attacks on AES, exploit nonce reuse in ECDSA, and apply lattice reduction to recover secrets from too few shares. This path assumes you are comfortable with encoding, hashing, and basic RSA.
- Step 01
RSA Factoring Attacks
Textbook RSA is secure; the implementations in CTFs are not. These challenges exploit specific structural weaknesses: a tiny exponent that lets you take a plain cube root, a smooth p-1 that falls to Pollard's algorithm, a leaked sum and product of the primes, and moduli that share a prime factor recoverable by GCD.
- Step 02
Broken Key Generation and Recovery
When key generation uses bad randomness or the key file is partially corrupted, the private key becomes recoverable. These challenges make you exploit a weak exponent choice, reconstruct a damaged RSA key from its intact fields and the CRT relationships, and rebuild missing prime factors from partial data.
- Step 03
Symmetric and Mode Attacks
Symmetric crypto fails when a mode is misused. AES-ABC chains blocks in a broken way you can unwind, Double DES collapses to a meet-in-the-middle search, ChaCha Slide loses integrity when you tamper with a Poly1305 ciphertext, and XtraORdinary falls to the parity property of repeated XOR.
- Step 04
Side-Channel and Oracle Attacks
You do not always attack the algorithm directly. Power analysis correlates simulated power traces against predicted SubBytes outputs to recover an AES key byte by byte, a compression oracle leaks plaintext through ciphertext length, and a biased ECDSA nonce gives up the private key across signatures.
- Step 05
Lattices and Advanced Number Theory
The hardest crypto challenges reach for heavier mathematics. You reconstruct secrets from partial outputs with the Chinese Remainder Theorem and polynomial interpolation, tame fast-growing sequences with matrix exponentiation, and apply lattice-based attacks to recover a Shamir secret from insufficient shares.