The Action Circuit configuration uses 10 advice columns. It contains:
- a single EccConfig (10 advice columns);
- two SinsemillaConfigs (5 advice columns each);
- two MerkleConfigs (5 advice columns each);
- a PoseidonConfig, (4 advice columns);
- a PLONKConfig for standard PLONK operations (3 advice columns);
and some infrastructure to handle public inputs (subject to change
at the time of commit).
The 5-column configs are placed side-by-side in the circuit to
optimize space usage.
Gate creation is delegated to the configure() function of each
respective Chip.
The Default Circuit sets all fields to None. This is used as a
placeholder in src/builder.rs.
The circuit in the Circuit::round_trip() test has been filled in.
This was previously creating an extra advice column. Instead, we
should pass in all required advice columns as inputs.
Co-authored-by: Jack Grigg <jack@electriccoin.co>
- `halo2::plonk::{create_proof, verify_proof}` now take instance columns
as slices of values.
- `halo2::plonk::Permutation` has been replaced by a global permutation,
to which columns can be added with `ConstraintSystem::enable_equality`.
- The introduction of blinding rows means that various tests now require
larger circuit parameters.
The coordinate check for an element decomposed using a running sum
is enforced by mul_fixed::Config::running_sum_coords_gate().
Co-authored-by: Jack Grigg <jack@electriccoin.co>
Selectors previously used in the witness_scalar_* APIs, such as
q_scalar_fixed and q_scalar_fixed_short, are now removed. The
remaining selectors have been renamed for clarity.
The coordinates check for scalars decomposed using a running sum
has been moved into the mul_fixed.rs file, instead of being
duplicated in both mul_fixed::base_field_elem and mul_fixed::short.
The decompose_scalar_fixed() method is now only used in
mul_fixed::full_width, and has been moved there.
These are now provided as inputs to the witness_decompose() and
copy_decompose() methods. This allows us to reuse the same config
for different word/window lengths, avoiding a duplicate constraint
creation.
Co-authored-by: Jack Grigg <jack@electriccoin.co>
In the Orchard protocol, only the NullifierK fixed base in used in
scalar multiplication with a base field element.
The mul_fixed_base_field_elem() API does not have to accept fixed
bases other than NullifierK; conversely, NullifierK does not have
to work with the full-width mul_fixed() API.
This decomposes a field element into K-bit windows using a
running sum. Each step of the running sum is range-constrained.
In strict mode, the final output of the running sum is constrained
to be zero.
This helper asserts K <= 3.
The mul_fixed regions use complete addition on the last window,
and incomplete addition on all other windows. However, the complete
addition does not depend on any offsets in the incomplete addition
region, and can be separated into a disjoint region. Since incomplete
addition uses only four advice columns, while complete addition uses
nine, separating the regions would allow the layouter to optimise
their placement.
Co-authored-by: Jack Grigg <jack@electriccoin.co>
We can use the three-bit existing running sum decomposition to
constrain alpha_0 to be within 130 bits. This removes the need for
a 10-bit lookup decomposition of alpha_0.
Co-authored-by: Daira Hopwood <daira@jacaranda.org>
The differences between the final iteration and prior iterations are:
- The final iteration does not constrain (x_T, y_T) to propagate down.
- The final iteration constrains an assigned y_A output instead of a
derived y_A from the next iteration's variables.
We also swap the init_y constraint to match the book.
Co-authored-by: therealyingtong <yingtong@z.cash>
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.
On the LSB of the scalar, we assign a point (x,y) = (x_p, -y_p)
if LSB = 0, and (0,0) otherwise. This if/else condition must be
enforced.
Co-authored-by: Sean Bowe <ewillbefull@gmail.com>
Using these in `OrchardFixedBases::{generator, u}` instead of the
`impl From<OrchardFixedBasesFull> for OrchardFixedBase` means we avoid
computing the Lagrange coefficients for the generator (which were then
immediately dropped).
This decreases proving time in the Action circuit by 53%.
In Orchard nullifier derivation, we multiply the fixed base
K^Orchard by a value encoded as a base field element. This commit
introduces an API that allows using a base field element as the
"scalar" in fixed-base scalar multiplication.
The API currently assumes that the base field element is output by
another instruction (i.e. there is no instruction to directly
witness it).
The magnitude of the short signed scalar must be 64 bits. We decompose
the magnitude into 22 3-bit windows and check that each window is in
the 3-bit range.
However, since the first 21 windows have already accounted for 63 bits,
the last window is constrained to be a single bit.
Simplify the canonicity check for variable-base scalar multiplication,
by range-checking the low 130 bits rather than the low 127 bits.
Signed-off-by: Daira Hopwood <daira@jacaranda.org>
Co-authored-by: ying tong <yingtong@z.cash>
Fixed-base scalar mul makes use of the add_incomplete and add
instructions internally. The full-width and short signed share
some common logic, which is captured in chip::mul_fixed.rs.
The signed short variant introduces additional logic to handle
the scalar's sign. This is done in the submodule mul_fixed::short.
A scalar used in fixed-base scalar mul needs to be decomposed into
windows to use with the fixed-base window table. Both full-width
and short signed scalars share some logic (captured in the function
decompose_scalar_fixed()).
A short signed scalar introduces additional logic: its magnitude is
decomposed, and its sign is separately witnessed. This is handled
in the submodule witness_scalar_fixed::short.
This uses the complete addition instruction internally. The module
is split up into mul::incomplete.rs and mul::complete.rs, where
mul::incomplete handles the incomplete additions used in the
starting rounds of the variable-base scalar mul algorithm, and
mul::complete handles the complete additions in the final rounds.
Incomplete additions are broken into "hi" and "lo" halves and
processed on the same rows across different columns. This is an
optimization to make full use of the advice columns in this
instruction.
- document that find_zs_and_us is not meant to be used anywhere
- use F::zero() instead of F::default() in constants/util.rs
- use personalisations from constants in spec.rs
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().
Also introduce a "strict" mode for the full-length lookup, where
"true" requires the field element to be within num_words * K bits,
whereas "false" does not.
hash_piece() is an internal API, which means its caller hash_message()
is working in the same region. We rely on the caller to have already
assigned each piece's initial x_a at the correct offset before making
the call to hash_piece().
Co-authored-by: Jack Grigg <jack@electriccoin.co>
This toggles the assignment of q_s2 on the last row of each piece.
We assign q_s2 = 2 on the last row of the final piece, and q_s2 = 0
on the last row of other pieces.
This allows us to process the final_piece in the main loop together
with the other pieces.
Co-authored-by: Jack Grigg <jack@electriccoin.co>
Also, GeneratorTable::configure() was not being called in the main
SinsemillaChip::configure(), which meant the lookup argument had
not been activated. This has now been fixed.
Co-authored-by: Jack Grigg <jack@electriccoin.co>
witness_message() witnesses a full message given a bitstring.
The other two APIs, witness_message_piece_bitstring() and
witness_message_piece_field(), both witness a message piece, i.e.
part of a message that fits within a single base field element.
witness_message_piece_bitstring() takes in a bitstring, while
witness_message_piece_field() takes in a field element. In the
latter case, the number of words encoded must be specified.
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.
This decomposes a field element into K-bit words and constrains each
word's range by looking it up in a K-bit lookup table.
The field element is broken down using a running sum. All interstitial
values of the running sum are returned.
Fixed points are represented by precomputed window tables. These
are not "initialized" in the circuit at any single point, but are
loaded into fixed columns at the offsets where the fixed points
are used.
Thus, we don't need FixedPoint and get_fixed() in the circuit.
Similarly, we can remove FixedPointShort and get_fixed_short().
therealyingtong
Kris Nuttycombe
str4d
Kris Nuttycombe
Kris Nuttycombe
Daira Hopwood
ebfull