zakirkun Insecure Diffie-Hellman Parameters
Overview
Diffie-Hellman key exchange with weak parameters is vulnerable to precomputation attacks (LogJam attack, 2015). Common issues:
- DH groups < 2048 bits (export-grade: 512/768/1024 bits)
- Using standard well-known small prime groups (precomputed NFS databases)
- Reusing the same DH parameters across many connections (static DH)
Remediation
- Use DH groups ≥ 2048 bits or RFC 7919 FFDHE groups
- Prefer ECDH (Elliptic Curve DH) with P-256/P-384/X25519 — more efficient and secure
- Generate unique DH parameters per deployment