Module hypertree 

Hypertree: a d-layer tree of XMSS trees for many-time signing. Hypertree: a multi-layer tree-of-XMSS-trees structure (FIPS 205, Algorithms 12-13).

The hypertree is a d-layer construction where each layer consists of XMSS trees of height h'. The leaves of each upper-layer XMSS tree certify the roots of lower-layer trees, forming a hierarchy with total height h = d * h'.

This structure allows the scheme to support 2^h FORS signing key pairs while keeping each individual XMSS tree small (only 2^h' leaves). The hypertree signature consists of d XMSS signatures, one per layer, chained from the bottom (layer 0) to the top (layer d - 1).

Functions

ht_sign

Sign a message using the hypertree.

ht_sign_into

Streaming variant of ht_sign — writes the D * (LEN + H') * N byte hypertree signature into the start of out (which must be at least that size).

ht_verify

Verify a hypertree signature.