pedersen-commitment

Pedersen Commitments

A step-by-step Rust implementation of Pedersen Commitment Schemes on the BLS12-381 curve, built for learning.

What is a Pedersen Commitment?

A commitment scheme is like putting a value in a locked box:

• Commit: lock your value inside — nobody can see it (hiding)
• Reveal: open the box later — you can't swap the value (binding)

The Pedersen formula: C = v·G + r·H

Symbol	Meaning
v	The secret value you're committing to
r	A random blinding factor (hides v)
G	Standard BLS12-381 G1 generator
H	Second generator with unknown discrete log
C	The commitment (a curve point)

Structure

File	What it covers
generator.rs	Setting up G and H
commit.rs	commit(v, r) and verify(v, r, C)
homomorphic.rs	C1 + C2 = Commit(v1+v2, r1+r2)

Key Properties

• Hiding: Same value + different r → completely different commitments
• Binding: Can't find another (v', r') that opens to the same C (requires solving discrete log)
• Homomorphic: Add/subtract commitments without revealing the values inside

Real-World Usage

This is the core primitive behind:

• Monero — hides transaction amounts
• Mimblewimble — confidential transactions
• Bulletproofs — range proofs
• ZK-SNARKs — as a building block for polynomial commitments

Run

cargo run    # see all 3 parts in action
cargo test   # run all 7 unit tests

Dependencies

Uses ark-bls12-381 — the same curve used in Ethereum's BLS signatures.