Spongos

Spongos is a term used in cryptography to describe a family of sponge-based authenticated encryption primitives. Derived from sponge function concepts, spongos operates with a fixed-size internal state that absorbs input data, including plaintext and associated data, and squeezes output to produce ciphertext and authentication tags. In practice, spongos implementations use a duplex or sponge construction, where data is absorbed in blocks, a permutation is applied to update the state, and output is generated. This allows streaming processing and combines confidentiality with integrity in a single primitive.

Construction and operation typically specify a state size, a rate (the portion of the state that can be processed per step), and a permutation function. Encryption proceeds by absorbing key material and plaintext into the state, applying the permutation, and outputting ciphertext; decryption follows the inverse process. Associated data can be authenticated without encryption. Padding rules ensure proper alignment of inputs. The security model relies on the underlying permutation and the sponge framework to provide indistinguishability of ciphertexts and resistance to forgery under appropriate parameter choices.

Usage and context: Spongos have been proposed for lightweight secure messaging and embedded devices as an all-in-one alternative to separate encryption and MAC schemes. They are described primarily in theoretical works or in protocol designs that favor streaming operation and simplicity, rather than as a widely adopted standard.

History and notes: The term “spongos” appears in cryptographic literature as a descriptive name for sponge-based authenticated encryption schemes. There is no single standardized algorithm by that exact name; implementations vary in state size, rate, permutation, and padding. As with any cryptographic primitive, security depends on careful parameter selection and rigorous analysis.

See also: Sponge function, Duplex construction, Authenticated encryption, Cryptographic sponge.