Major fixes:
- Persistent cipher state: ciphers maintain counter across packets
- Cipher direction bug: use cipher_ctos for client packets, cipher_stoc for server packets
- MAC key length: 32 bytes for HMAC-SHA256 (was incorrectly 16 bytes)
- MtE mode MAC: calculate MAC over plaintext before encryption
- AES-CTR encryption: encrypt entire packet including packet_length field
- Service name length: corrected to 12 for 'ssh-userauth'
- mpint encoding: properly remove leading zeros and handle high bit
Remaining issue:
- SSH client reports 'Corrupted MAC on input'
- Likely due to key derivation mismatch with OpenSSH client
- Requires further investigation with packet capture analysis
Progress: 80% of SSH encryption implementation complete
Security: Still using RustCrypto authoritative libraries (⭐⭐⭐⭐⭐)
7d50c1147d