Understanding Asymmetric Cryptography in Secure File Exchange

Public/Private keys

Use the recipient’s public key to encrypt, and the sender’s private key to sign. Recipients verify with the sender’s public key and decrypt with their private key.

Hybrid encryption

Encrypt the data with a symmetric key (fast), then encrypt that key with the recipient’s public key (secure). This is the standard approach in production.

Key rotation

Plan for periodic rotation and revocation. Store metadata with algorithms and versions to support seamless upgrades.

Threat modeling

Protect against replay attacks, tampering, and impersonation. Add nonces, timestamps, and integrity checks.