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deserialize uncompressed
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@hujw77
hujw77 committed Nov 27, 2023
1 parent d523ec2 commit abec257
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Showing 4 changed files with 34 additions and 93 deletions.
77 changes: 0 additions & 77 deletions src/bls12381/Fp.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -163,81 +163,4 @@ library BLS12FP {
}
return Bls12Fp(output[0], output[1]);
}

/// @dev base^base % modulus
/// @param base Bls12Fp.
/// @param exp Bls12Fp.
/// @param modulus Bls12Fp.
/// @return Result of mod_exp.
function mod_exp(
Bls12Fp memory base,
Bls12Fp memory exp,
Bls12Fp memory modulus
)
internal
view
returns (Bls12Fp memory)
{
uint256[9] memory input;
input[0] = 0x40;
input[1] = 0x40;
input[2] = 0x40;
input[3] = base.a;
input[4] = base.b;
input[5] = exp.a;
input[6] = exp.b;
input[7] = modulus.a;
input[8] = modulus.b;
uint256[2] memory output;

assembly ("memory-safe") {
if iszero(staticcall(gas(), MOD_EXP, input, 288, output, 64)) {
let p := mload(0x40)
returndatacopy(p, 0, returndatasize())
revert(p, returndatasize())
}
}

return Bls12Fp(output[0], output[1]);
}

/// @dev base^base % modulus
/// @param base Bls12Fp.
/// @param exp uint256.
/// @param modulus Bls12Fp.
/// @return Result of mod_exp.
function mod_exp(Bls12Fp memory base, uint256 exp, Bls12Fp memory modulus) internal view returns (Bls12Fp memory) {
uint256[8] memory input;
input[0] = 0x40;
input[1] = 0x40;
input[2] = 0x40;
input[3] = base.a;
input[4] = base.b;
input[5] = exp;
input[6] = modulus.a;
input[7] = modulus.b;
uint256[2] memory output;

assembly ("memory-safe") {
if iszero(staticcall(gas(), MOD_EXP, input, 256, output, 64)) {
let p := mload(0x40)
returndatacopy(p, 0, returndatasize())
revert(p, returndatasize())
}
}

return Bls12Fp(output[0], output[1]);
}

// using quadratic residue
function find_y(Bls12Fp memory x) internal view returns (Bls12Fp memory) {
Bls12Fp memory y_square = add(mod_exp(x, 3, q()), b());
Bls12Fp memory y = mod_exp(y_square, qr(), q());
return y;
}

// pow(y, 2, q) == (x**3 + b.n) % q:
function is_on_curve(Bls12Fp memory x, Bls12Fp memory y) internal view returns (bool) {
return eq(mod_exp(y, 2, q()), add(mod_exp(x, 3, q()), b()));
}
}
12 changes: 12 additions & 0 deletions src/bls12381/Fp2.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,14 @@ library BLS12FP2 {
bytes private constant Z_PAD =
hex"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000";

function zero() internal pure returns (Bls12Fp2 memory) {
return Bls12Fp2(BLS12FP.zero(), BLS12FP.zero());
}

function b2() internal pure returns (Bls12Fp2 memory) {
return Bls12Fp2(Bls12Fp(0, 4), Bls12Fp(0, 4));
}

/// @dev Returns `true` if `x` is equal to `y`.
/// @param x Bls12Fp2.
/// @param y Bls12Fp2.
Expand All @@ -33,6 +41,10 @@ library BLS12FP2 {
return x.c0.is_zero() && x.c1.is_zero();
}

function is_valid(Bls12Fp2 memory self) internal pure returns (bool) {
return self.c0.is_valid() && self.c1.is_valid();
}

/// @dev Hash an arbitrary `msg` to `2` elements from field `Fp2`.
/// @param message A byte string containing the message to hash.
/// @return `2` of field elements.
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17 changes: 6 additions & 11 deletions src/bls12381/G1.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -94,33 +94,28 @@ library BLS12G1Affine {
}

// Take a 96 byte array and convert to a G1 point (x, y)
function deserialize(bytes memory g1) internal view returns (Bls12G1 memory) {
require(g1.length == 48, "!g1");
function deserialize(bytes memory g1) internal pure returns (Bls12G1 memory) {
require(g1.length == 96, "!g1");
bytes1 byt = g1[0];
bool c_flag = (byt >> 7) & 0x01 == 0x01;
bool b_flag = (byt >> 6) & 0x01 == 0x01;
bool a_flag = (byt >> 5) & 0x01 == 0x01;
if (a_flag && (!c_flag || b_flag)) {
revert("!flag");
}
require(c_flag, "uncompressed");
require(!c_flag, "compressed");

// Zero flags
g1[0] = byt & 0x1f;
Bls12Fp memory x = Bls12Fp(g1.slice_to_uint(0, 16), g1.slice_to_uint(16, 48));
Bls12Fp memory y = Bls12Fp(g1.slice_to_uint(48, 64), g1.slice_to_uint(64, 96));
if (b_flag) {
require(x.is_zero(), "!zero");
require(x.is_zero() && y.is_zero(), "!zero");
return zero();
}

Bls12Fp memory y = x.find_y();

// Require elements less than field modulus
require(x.is_valid() && y.is_valid(), "!fp");

if (y.add(y).gt(BLS12FP.q()) != a_flag) {
y = BLS12FP.q().sub(y);
}
require(x.is_valid() && y.is_valid(), "!pnt");

// Convert to G1
Bls12G1 memory p = Bls12G1(x, y);
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21 changes: 16 additions & 5 deletions src/bls12381/G2.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,10 @@ library BLS12G2Affine {
bytes1 private constant INFINITY_FLAG = bytes1(0x40);
bytes1 private constant Y_FLAG = bytes1(0x20);

function zero() internal pure returns (Bls12G2 memory) {
return Bls12G2(BLS12FP2.zero(), BLS12FP2.zero());
}

/// @dev Returns `true` if `x` is equal to `y`.
/// @param a Bls12G2.
/// @param b Bls12G2.
Expand Down Expand Up @@ -126,18 +130,25 @@ library BLS12G2Affine {
function deserialize(bytes memory g2) internal pure returns (Bls12G2 memory) {
require(g2.length == 192, "!g2");
bytes1 byt = g2[0];
require(byt & COMPRESION_FLAG == 0, "compressed");
require(byt & INFINITY_FLAG == 0, "infinity");
require(byt & Y_FLAG == 0, "y_flag");

g2[0] = byt & 0x1f;
bool c_flag = (byt >> 7) & 0x01 == 0x01;
bool b_flag = (byt >> 6) & 0x01 == 0x01;
bool a_flag = (byt >> 5) & 0x01 == 0x01;
if (a_flag && (!c_flag || b_flag)) {
revert("!flag");
}
require(!c_flag, "compressed");

// Convert from array to FP2
Bls12Fp memory x_imaginary = Bls12Fp(g2.slice_to_uint(0, 16), g2.slice_to_uint(16, 48));
Bls12Fp memory x_real = Bls12Fp(g2.slice_to_uint(48, 64), g2.slice_to_uint(64, 96));
Bls12Fp memory y_imaginary = Bls12Fp(g2.slice_to_uint(96, 112), g2.slice_to_uint(112, 144));
Bls12Fp memory y_real = Bls12Fp(g2.slice_to_uint(144, 160), g2.slice_to_uint(160, 192));

if (b_flag) {
require(x_imaginary.is_zero() && x_real.is_zero() && y_imaginary.is_zero() && y_real.is_zero(), "!zero");
return zero();
}

// Require elements less than field modulus
require(x_imaginary.is_valid() && x_real.is_valid() && y_imaginary.is_valid() && y_real.is_valid(), "!pnt");

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