AEADalgoritmer

AEADalgoritmer are cryptographic primitives that provide confidentiality and integrity for both the message and its associated data. They implement authenticated encryption with associated data (AEAD), producing ciphertext plus an authentication tag. The tag verifies both the ciphertext and the AAD during decryption. A nonce (IV) must be unique per key and message; reusing a nonce breaks secrecy and authenticity.

Common AEAD algorithms include AES-GCM and ChaCha20-Poly1305, which are widely deployed in TLS, SSH, IPsec, and disk encryption. Other examples are AES-CCM, AES-SIV, and EAX. The choice depends on hardware support, performance, and misuse resistance requirements. Tag lengths are typically 128 bits; keys are 128 or 256 bits, with 12-byte nonces being common for GCM and ChaCha20-Poly1305.

In practice, AEAD is used through standardized interfaces, for example NIST SP 800-38D for AES-GCM and RFC 7539 for ChaCha20-Poly1305; RFC 5116 describes a generic AEAD API. Implementations must ensure secret keys are handled in constant time where applicable, and nonces are never repeated with the same key. AAD allows protecting header information or other data that must be authenticated but not encrypted.

Security: AEAD schemes aim to provide IND-CCA-like security in their authenticated encryption notion, combining confidentiality and integrity in a single primitive.