pub fn base_2b(x: &[u8], b: usize, out_len: usize) -> Vec<u32>Expand description
Extract base-2^b digits from a byte string.
Implements Algorithm 4 of FIPS 205. Interprets the byte string x as a sequence
of b-bit unsigned integers in big-endian bit order and returns out_len digits,
each in the range [0, 2^b).
For the standard WOTS+ parameters (lg_w = 4, b = 4), this extracts nibbles.
It is also used by FORS to extract a-bit indices from the message digest.