AES Encryption & Decryption

This cryptographic tool implements Advanced Encryption Standard (AES) using the Web Crypto API, supporting key sizes of 128, 192, or 256 bits for varying security requirements. The encryption process converts plaintext into ciphertext through multiple rounds of substitution, permutation, and XOR operations as defined in the FIPS 197 specification. Each round applies byte substitution, row shifting, column mixing, and round key addition to achieve cryptographic strength.

Users provide a passphrase which undergoes PBKDF2 (Password-Based Key Derivation Function 2) with 100,000 iterations and SHA-256 hashing to generate the cryptographic key from human-readable input. The system employs GCM (Galois/Counter Mode) which provides both confidentiality through encryption and authenticity through built-in message authentication codes. Random initialization vectors ensure that identical plaintexts produce different ciphertexts, preventing pattern analysis attacks.

All cryptographic operations process locally within your browser's secure enclave using native WebCrypto implementations, preventing key or plaintext exposure to external servers or network transmission. This zero-knowledge architecture makes the tool suitable for encrypting sensitive messages, storing credentials securely, or protecting personal notes before cloud storage. The authenticated encryption mode also detects tampering attempts during decryption.