API encryption prtoects data during transmission using algorithms like AES, DES, and RSA. Testing verifies both the correctness and security of these encryption methods.

Symmetric Encryption

Symmetric encryption uses a single key for both encryption and decryption. Common algorithms include:

• DES
• 3DES
• AES
• Blowfish
• RC4/RC5/RC6

Key considerations:

1. The same key encrypts and decrypts data
2. Key distribution presents security challenges
3. Never implmeent sensitive operations like password encryption in client-side JavaScript

Asymmetric Encryption

Asymmetric encryption employs paired public/private keys:

• Public keys encrypt data
• Private keys decrypt data

Common algorithms:

• RSA
• ECC (for mobile)
• Diffie-Hellman
• DSA (to signatures)

Implementation flow:

1. Generate key pair (public + private)
2. Share public key with communication partners
3. Partners encrypt data with public key
4. Decrypt data with private key

Digital Signatures

Digital signatures combine hashing with asymmetric encryption to verify:

• Data authenticity
• Message integrity
• Non-repudiation