HMACiga

HMACiga is a family of message authentication codes derived from the HMAC construction, augmented with an auxiliary transformation called iga (Integrity-Generating Augment). It is designed to provide data authenticity and integrity for messages under a secret key while enabling incremental, streaming-style verification. HMACiga is discussed in theoretical and experimental contexts as a potential alternative or extension to standard HMAC.

Design and operation: HMACiga retains the general two-stage structure of HMAC (inner and outer hashing) but replaces the conventional key padding with an iga-based key-mixing function. The secret key K is processed by iga to produce an inner-key Ki and an outer-key Ko. The message is fed incrementally into an inner hasher initialized with Ki, yielding an inner digest. A final outer hashing step uses Ko and the inner digest to produce the authentication tag. The iga layer is intended to support flexible key derivation across message segments and to allow configuration for different security and performance profiles.

Security considerations: The security of HMACiga relies on the standard assumptions underlying HMAC, primarily that the underlying hash function behaves as a pseudorandom function when keyed. The iga transformation is designed to provide domain separation between inner and outer computations and to mitigate certain classes of length-extension or padding-related weaknesses in some hash families. Verification remains straightforward: a party with the same secret key can recompute the tag and compare it to the provided value.

Applications and variants: HMACiga can be used for API authentication, integrity protection in streaming protocols, and data integrity checks in storage systems. Variants may offer different tag lengths or performance characteristics tailored to specific environments. See also HMAC, MAC, and hash-based message authentication codes.