Cryptopals Challenges — Rust

An ongoing project working through the Cryptopals Crypto Challenges in Rust. The goal is to build low-level cryptographic primitives and attack implementations from scratch, developing a grounded understanding of how real-world cryptography works and breaks.

No high-level crypto libraries are used for the core challenge logic — only foundational encoding utilities (hex, base64) and Rust's standard library.

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Project Structure

src/
├── main.rs
└── set_N/
    ├── mod.rs
    └── ex_N.rs

Each set lives in its own module (set_1, set_2, ...) and each exercise in its own file. Auxiliary helpers shared across a set are kept in mod.rs.

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Progress

Set 1 — Basics

Foundational encoding and XOR-based cryptanalysis.

#	Title	Status
1	Convert hex to Base64	✅ Done
2	Fixed XOR	✅ Done
3	Single-byte XOR cipher	🔄 In progress
4	Detect single-character XOR	⬜ Pending
5	Implement repeating-key XOR	⬜ Pending
6	Break repeating-key XOR	⬜ Pending
7	AES in ECB mode	⬜ Pending
8	Detect AES in ECB mode	⬜ Pending

Set 2 — Block Crypto

CBC mode, padding, and the first padding oracle.

#	Title	Status
9	Implement PKCS#7 padding	⬜ Pending
10	Implement CBC mode	⬜ Pending
11	An ECB/CBC detection oracle	⬜ Pending
12	Byte-at-a-time ECB decryption (Simple)	⬜ Pending
13	ECB cut-and-paste	⬜ Pending
14	Byte-at-a-time ECB decryption (Harder)	⬜ Pending
15	PKCS#7 padding validation	⬜ Pending
16	CBC bitflipping attacks	⬜ Pending

Set 3 — Block & Stream Crypto

Breaking CBC and introducing stream ciphers.

#	Title	Status
17	The CBC padding oracle	⬜ Pending
18	Implement CTR, the stream cipher mode	⬜ Pending
19	Break fixed-nonce CTR mode using substitutions	⬜ Pending
20	Break fixed-nonce CTR statistically	⬜ Pending
21	Implement the MT19937 Mersenne Twister RNG	⬜ Pending
22	Crack an MT19937 seed	⬜ Pending
23	Clone an MT19937 RNG from its output	⬜ Pending
24	Create the MT19937 stream cipher and break it	⬜ Pending

Set 4 — Stream Crypto & Randomness

SHA-1 and MD4 length extension, CTR bitflipping.

#	Title	Status
25	Break "random access read/write" AES CTR	⬜ Pending
26	CTR bitflipping	⬜ Pending
27	Recover the key from CBC with IV=Key	⬜ Pending
28	Implement a SHA-1 keyed MAC	⬜ Pending
29	Break a SHA-1 keyed MAC using length extension	⬜ Pending
30	Break an MD4 keyed MAC using length extension	⬜ Pending
31	Implement and break HMAC-SHA1 with an artificial timing leak	⬜ Pending
32	Break HMAC-SHA1 with a slightly less artificial timing leak	⬜ Pending

Set 5 — Diffie-Hellman & Friends

Public-key fundamentals, MITM, SRP.

#	Title	Status
33	Implement Diffie-Hellman	⬜ Pending
34	Implement a MITM key-fixing attack on Diffie-Hellman with parameter injection	⬜ Pending
35	Implement DH with negotiated groups, and break with malicious g parameters	⬜ Pending
36	Implement Secure Remote Password (SRP)	⬜ Pending
37	Break SRP with a zero key	⬜ Pending
38	Offline dictionary attack on simplified SRP	⬜ Pending
39	Implement RSA	⬜ Pending
40	Implement an E=3 RSA broadcast attack	⬜ Pending

Set 6 — RSA & DSA

Signature forgery, padding oracles on RSA.

#	Title	Status
41	Implement unpadded message recovery oracle	⬜ Pending
42	Bleichenbacher's e=3 RSA attack	⬜ Pending
43	DSA key recovery from nonce	⬜ Pending
44	DSA nonce recovery from repeated nonce	⬜ Pending
45	DSA parameter tampering	⬜ Pending
46	RSA parity oracle	⬜ Pending
47	Bleichenbacher's PKCS 1.5 Padding Oracle (Simple)	⬜ Pending
48	Bleichenbacher's PKCS 1.5 Padding Oracle (Complete)	⬜ Pending

Set 7 — Hashing

Hash function internals and collision attacks.

#	Title	Status
49	CBC-MAC message forgery	⬜ Pending
50	Hashing with CBC-MAC	⬜ Pending
51	Compression ratio side-channel attacks	⬜ Pending
52	Iterated hash function multicollisions	⬜ Pending
53	Kelsey and Schneier's expandable messages	⬜ Pending
54	Kelsey and Kohno's nostradamus attack	⬜ Pending
55	MD4 collisions	⬜ Pending
56	RC4 single-byte biases	⬜ Pending

Set 8 — Abstract Algebra

Elliptic curves, GCM, and advanced number theory attacks.

#	Title	Status
57	Diffie-Hellman Revisited: Small Subgroup Confinement	⬜ Pending
58	Pollard's Method for Catching Kangaroos	⬜ Pending
59	Elliptic Curve Diffie-Hellman and Invalid-Curve Attacks	⬜ Pending
60	Single-Coordinate Ladders and Insecure Twists	⬜ Pending
61	Duplicate-Signature Key Selection in ECDSA (and RSA)	⬜ Pending
62	Key-Recovery Attacks on ECDSA with Biased Nonces	⬜ Pending
63	Key-Recovery Attacks on GCM with Repeated Nonces	⬜ Pending
64	Key-Recovery Attacks on GCM with a Truncated MAC	⬜ Pending

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What This Demonstrates

• Rust systems programming: manual memory layout, ownership-driven API design, zero-copy byte manipulation
• Cryptographic fundamentals: block/stream ciphers, MACs, public-key systems, hash functions — implemented from scratch
• Adversarial thinking: every exercise is an attack, not a construction — breaking things to understand how they work
• Incremental design: a growing codebase with reusable primitives built up exercise by exercise

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Running

cargo run

Individual exercise entry points are exposed via set_N::ex_N::run() and called from main.rs.