At certain points in the circuit, we need to constrain cells in
advice columns to equal a fixed constant. Instead of defining a
new fixed column for each constant, we pass around a single
shared by all chips, that is included in the permutation over all
advice columns.
This lets us load all needed constants into a single column and
directly constrain advice cells with an equality constraint.
This has three const generic parameters: PATH_LENGTH, K, MAX_WORDS.
PATH_LENGTH is the length of the Merkle path being hashed. K and
MAX_WORDS parameterize the internal Sinsemilla instance used in
hashing the path.
These instructions were not making any assignments; instead, they
were calling through to witness_message_piece_field().
This PR also renames the witness_message_piece_field() instruction
to witness_message_piece().
This defines a Sinsemilla message in terms of pieces and subpieces.
This is useful when decomposing field elements and packing them
into K-bit messages.
SinsemillaInstructions has two const generic parameters: K, which
is the number of bits in each word of the hash, and MAX_WORDS,
which is the maximum number of words the hash can process.
For Orchard, K = 10, MAX_WORDS = 253.
therealyingtong
Jack Grigg