20 KiB
C API
New features
void mclBn_setOriginalG2cofactor(int enable);
Use faster multiplication of G2
with cofactor if enable = 1
.
This is enabled if mclBn_setMapToMode(MCL_MAP_TO_MODE_ETH2)
.
if enable = 0
, then the fast algorithm (mulByCofactorBLS12) is used.
Minimum sample
sample/pairing_c.c is a sample of how to use BLS12-381 pairing.
cd mcl
make -j4
make bin/pairing_c.exe && bin/pairing_c.exe
Header and libraries
To use BLS12-381, include mcl/bn_c384_256.h
and link
- libmclbn384_256.{a,so}
- libmcl.{a,so} ; core library
384_256
means the max bit size of Fp
is 384 and that size of Fr
is 256.
Notation
The elliptic equation of a curve E is E: y^2 = x^3 + b
.
Fp
; a finite field of a prime orderp
, where curves is defined over.Fr
; a finite field of a prime orderr
.Fp2
; the field extension over Fp with degree 2. Fp[i] / (i^2 + 1).Fp6
; the field extension over Fp2 with degree 3. Fp2[v] / (v^3 - Xi) where Xi = i + 1.Fp12
; the field extension over Fp6 with degree 2. Fp6[w] / (w^2 - v).G1
; the cyclic subgroup of E(Fp).G2
; the cyclic subgroup of the inverse image of E'(Fp^2) under a twisting isomorphism from E' to E.GT
; the cyclie subgroup of Fp12.G1
,G2
andGT
have the orderr
.
The pairing e: G1 x G2 -> GT is the optimal ate pairing.
mcl treats G1
and G2
as an additive group and GT
as a multiplicative group.
mclSize
;unsigned int
if WebAssembly elsesize_t
Curve Parameter
r = |G1| = |G2| = |GT|
curveType | b | r and p |
---|---|---|
BN254 | 2 | r = 0x2523648240000001ba344d8000000007ff9f800000000010a10000000000000d p = 0x2523648240000001ba344d80000000086121000000000013a700000000000013 |
BLS12-381 | 4 | r = 0x73eda753299d7d483339d80809a1d80553bda402fffe5bfeffffffff00000001 p = 0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffaaab |
BN381 | 2 | r = 0x240026400f3d82b2e42de125b00158405b710818ac000007e0042f008e3e00000000001080046200000000000000000d p = 0x240026400f3d82b2e42de125b00158405b710818ac00000840046200950400000000001380052e000000000000000013 |
Structures
mclBnFp
This is a struct of Fp
. The value is stored as Montgomery representation.
mclBnFr
This is a struct of Fr
. The value is stored as Montgomery representation.
mclBnFp2
This is a struct of Fp2
which has a member mclBnFp d[2]
.
An element x
of Fp2
is represented as x = d[0] + d[1] i
where i^2 = -1
.
mclBnG1
This is a struct of G1
which has three members x
, y
, z
of type mclBnFp
.
An element P
of G1
is represented as P = [x:y:z]
of a Jacobi coordinate.
mclBnG2
This is a struct of G2
which has three members x
, y
, z
of type mclBnFp2
.
An element Q
of G2
is represented as Q = [x:y:z]
of a Jacobi coordinate.
mclBnGT
This is a struct of GT
which has a member mclBnFp d[12]
.
sizeof
library | MCLBN_FR_UNIT_SIZE | MCLBN_FP_UNIT_SIZE | sizeof Fr | sizeof Fp |
---|---|---|---|---|
libmclbn256.a | 4 | 4 | 32 | 32 |
libmclbn384_256.a | 4 | 6 | 32 | 48 |
libmclbn384.a | 6 | 6 | 48 | 48 |
Thread safety
All functions except for initialization and changing global setting are thread-safe.
Initialization
Initialize mcl library. Call this function at first before calling the other functions.
int mclBn_init(int curve, int compiledTimeVar);
curve
; specify the curve type- MCL_BN254 ; BN254 (a little faster if including
mcl/bn_c256.h
and linkinglibmclbn256.{a,so}
) - MCL_BN_SNARK1 ; the same parameter used in libsnark
- MCL_BLS12_381 ; BLS12-381
- MCL_BN381_1 ; BN381 (include
mcl/bn_c384.h
and linklibmclbn384.{a,so}
)
- MCL_BN254 ; BN254 (a little faster if including
compiledTimeVar
; setMCLBN_COMPILED_TIME_VAR
, which macro is used to make sure that the values are the same when the library is built and used.- return 0 if success.
- This is not thread safe.
Global setting
int mclBn_setMapToMode(int mode);
The map-to-G2 function if mode = MCL_MAP_TO_MODE_HASH_TO_CURVE
.
Control to verify that a point of the elliptic curve has the order r
.
This function affects setStr()
and deserialize()
for G1/G2.
void mclBn_verifyOrderG1(int doVerify);
void mclBn_verifyOrderG2(int doVerify);
- verify if
doVerify
is 1 or does not. The default parameter is 0 because the cost of verification is not small. - Set
doVerify = 1
if considering subgroup attack is necessary. - This is not thread safe.
Setter / Getter
Clear
Set x
is zero.
void mclBnFr_clear(mclBnFr *x);
void mclBnFp_clear(mclBnFp *x);
void mclBnFp2_clear(mclBnFp2 *x);
void mclBnG1_clear(mclBnG1 *x);
void mclBnG2_clear(mclBnG2 *x);
void mclBnGT_clear(mclBnGT *x);
Set x
to y
.
void mclBnFp_setInt(mclBnFp *y, mclInt x);
void mclBnFr_setInt(mclBnFr *y, mclInt x);
void mclBnGT_setInt(mclBnGT *y, mclInt x);
Set buf[0..bufSize-1]
to x
with masking according to the following way.
int mclBnFp_setLittleEndian(mclBnFp *x, const void *buf, mclSize bufSize);
int mclBnFr_setLittleEndian(mclBnFr *x, const void *buf, mclSize bufSize);
- set x = buf[0..bufSize-1] as little endian
- x &= (1 << bitLen(r)) - 1
- if (x >= r) x &= (1 << (bitLen(r) - 1)) - 1
- always return 0
Set (buf[0..bufSize-1]
mod p
or r
) to x
.
int mclBnFp_setLittleEndianMod(mclBnFp *x, const void *buf, mclSize bufSize);
int mclBnFr_setLittleEndianMod(mclBnFr *x, const void *buf, mclSize bufSize);
- return 0 if bufSize <= (sizeof(*x) * 8 * 2) else -1
Get little endian byte sequence buf
corresponding to x
mclSize mclBnFr_getLittleEndian(void *buf, mclSize maxBufSize, const mclBnFr *x);
mclSize mclBnFp_getLittleEndian(void *buf, mclSize maxBufSize, const mclBnFp *x);
- write
x
tobuf
as little endian - return the written size if sucess else 0
- NOTE:
buf[0] = 0
and return 1 ifx
is zero.
Serialization
Serialize
mclSize mclBnFr_serialize(void *buf, mclSize maxBufSize, const mclBnFr *x);
mclSize mclBnG1_serialize(void *buf, mclSize maxBufSize, const mclBnG1 *x);
mclSize mclBnG2_serialize(void *buf, mclSize maxBufSize, const mclBnG2 *x);
mclSize mclBnGT_serialize(void *buf, mclSize maxBufSize, const mclBnGT *x);
mclSize mclBnFp_serialize(void *buf, mclSize maxBufSize, const mclBnFp *x);
mclSize mclBnFp2_serialize(void *buf, mclSize maxBufSize, const mclBnFp2 *x);
- serialize
x
intobuf[0..maxBufSize-1]
- return written byte size if success else 0
Serialization format
Fp
(resp.Fr
) ; a little endian byte sequence with a fixed size- the size is the return value of
mclBn_getFpByteSize()
(resp.mclBn_getFpByteSize()
).
- the size is the return value of
G1
; a compressed fixed size- the size is equal to
mclBn_getG1ByteSize()
(=mclBn_getFpByteSize()
).
- the size is equal to
G2
; a compressed fixed size- the size is equal to
mclBn_getG1ByteSize() * 2
.
- the size is equal to
pseudo-code to serialize of P
of G1
(resp. G2
)
size = mclBn_getG1ByteSize() # resp. mclBn_getG1ByteSize() * 2
if P is zero:
return [0] * size
else:
P = P.normalize()
s = P.x.serialize()
# x in Fp2 is odd <=> x.a is odd
if P.y is odd: # resp. P.y.d[0] is odd
s[byte-length(s) - 1] |= 0x80
return s
Ethereum serialization mode for BLS12-381
void mclBn_setETHserialization(int ETHserialization);
- serialize according to serialization of BLS12-381 if BLS12-381 is used and
ETHserialization = 1
(default 0).
Deserialize
mclSize mclBnFr_deserialize(mclBnFr *x, const void *buf, mclSize bufSize);
mclSize mclBnG1_deserialize(mclBnG1 *x, const void *buf, mclSize bufSize);
mclSize mclBnG2_deserialize(mclBnG2 *x, const void *buf, mclSize bufSize);
mclSize mclBnGT_deserialize(mclBnGT *x, const void *buf, mclSize bufSize);
mclSize mclBnFp_deserialize(mclBnFp *x, const void *buf, mclSize bufSize);
mclSize mclBnFp2_deserialize(mclBnFp2 *x, const void *buf, mclSize bufSize);
- deserialize
x
frombuf[0..bufSize-1]
- return read size if success else 0
String conversion
Get string
mclSize mclBnFr_getStr(char *buf, mclSize maxBufSize, const mclBnFr *x, int ioMode);
mclSize mclBnG1_getStr(char *buf, mclSize maxBufSize, const mclBnG1 *x, int ioMode);
mclSize mclBnG2_getStr(char *buf, mclSize maxBufSize, const mclBnG2 *x, int ioMode);
mclSize mclBnGT_getStr(char *buf, mclSize maxBufSize, const mclBnGT *x, int ioMode);
mclSize mclBnFp_getStr(char *buf, mclSize maxBufSize, const mclBnFp *x, int ioMode);
- write
x
tobuf
according toioMode
ioMode
- 10 ; decimal number
- 16 ; hexadecimal number
MCLBN_IO_EC_PROJ
; output as Jacobi coordinate
- return
strlen(buf)
if success else 0.
The meaning of the output of G1
.
0
; infinity1 <x> <y>
; affine coordinate4 <x> <y> <z>
; Jacobi coordinate- the element
<x>
ofG2
outputsd[0] d[1]
.
Set string
int mclBnFr_setStr(mclBnFr *x, const char *buf, mclSize bufSize, int ioMode);
int mclBnG1_setStr(mclBnG1 *x, const char *buf, mclSize bufSize, int ioMode);
int mclBnG2_setStr(mclBnG2 *x, const char *buf, mclSize bufSize, int ioMode);
int mclBnGT_setStr(mclBnGT *x, const char *buf, mclSize bufSize, int ioMode);
int mclBnFp_setStr(mclBnFp *x, const char *buf, mclSize bufSize, int ioMode);
- set
buf[0..bufSize-1]
tox
accoring toioMode
- return 0 if success else -1
If you want to use the same generators of BLS12-381 with zkcrypto then,
mclBnG1 P;
mclBnG1_setStr(&P, "1 3685416753713387016781088315183077757961620795782546409894578378688607592378376318836054947676345821548104185464507 1339506544944476473020471379941921221584933875938349620426543736416511423956333506472724655353366534992391756441569", 10);
mclBnG2 Q;
mclBnG2_setStr(&Q, "1 352701069587466618187139116011060144890029952792775240219908644239793785735715026873347600343865175952761926303160 3059144344244213709971259814753781636986470325476647558659373206291635324768958432433509563104347017837885763365758 1985150602287291935568054521177171638300868978215655730859378665066344726373823718423869104263333984641494340347905 927553665492332455747201965776037880757740193453592970025027978793976877002675564980949289727957565575433344219582");
Set random value
Set x
by cryptographically secure pseudo random number generator.
int mclBnFr_setByCSPRNG(mclBnFr *x);
int mclBnFp_setByCSPRNG(mclBnFp *x);
Change random generator function
void mclBn_setRandFunc(
void *self,
unsigned int (*readFunc)(void *self, void *buf, unsigned int bufSize)
);
self
; user-defined pointerreadFunc
; user-defined function, which writes randombufSize
bytes tobuf
and returnsbufSize
if success else returns 0.readFunc
must be thread-safe.
- Set the default random function if
self == 0
andreadFunc == 0
. - This is not thread safe.
Arithmetic operations
neg / inv / sqr / add / sub / mul / div of Fr
, Fp
, Fp2
, GT
.
void mclBnFr_neg(mclBnFr *y, const mclBnFr *x);
void mclBnFr_inv(mclBnFr *y, const mclBnFr *x);
void mclBnFr_sqr(mclBnFr *y, const mclBnFr *x);
void mclBnFr_add(mclBnFr *z, const mclBnFr *x, const mclBnFr *y);
void mclBnFr_sub(mclBnFr *z, const mclBnFr *x, const mclBnFr *y);
void mclBnFr_mul(mclBnFr *z, const mclBnFr *x, const mclBnFr *y);
void mclBnFr_div(mclBnFr *z, const mclBnFr *x, const mclBnFr *y);
void mclBnFp_neg(mclBnFp *y, const mclBnFp *x);
void mclBnFp_inv(mclBnFp *y, const mclBnFp *x);
void mclBnFp_sqr(mclBnFp *y, const mclBnFp *x);
void mclBnFp_add(mclBnFp *z, const mclBnFp *x, const mclBnFp *y);
void mclBnFp_sub(mclBnFp *z, const mclBnFp *x, const mclBnFp *y);
void mclBnFp_mul(mclBnFp *z, const mclBnFp *x, const mclBnFp *y);
void mclBnFp_div(mclBnFp *z, const mclBnFp *x, const mclBnFp *y);
void mclBnFp2_neg(mclBnFp2 *y, const mclBnFp2 *x);
void mclBnFp2_inv(mclBnFp2 *y, const mclBnFp2 *x);
void mclBnFp2_sqr(mclBnFp2 *y, const mclBnFp2 *x);
void mclBnFp2_add(mclBnFp2 *z, const mclBnFp2 *x, const mclBnFp2 *y);
void mclBnFp2_sub(mclBnFp2 *z, const mclBnFp2 *x, const mclBnFp2 *y);
void mclBnFp2_mul(mclBnFp2 *z, const mclBnFp2 *x, const mclBnFp2 *y);
void mclBnFp2_div(mclBnFp2 *z, const mclBnFp2 *x, const mclBnFp2 *y);
void mclBnGT_inv(mclBnGT *y, const mclBnGT *x); // y = a - bw for x = a + bw where Fp12 = Fp6[w]
void mclBnGT_sqr(mclBnGT *y, const mclBnGT *x);
void mclBnGT_mul(mclBnGT *z, const mclBnGT *x, const mclBnGT *y);
void mclBnGT_div(mclBnGT *z, const mclBnGT *x, const mclBnGT *y);
-
use
mclBnGT_invGeneric
for an element in Fp12 - GT. -
NOTE: The following functions do NOT return a GT element because GT is multiplicative group.
void mclBnGT_neg(mclBnGT *y, const mclBnGT *x);
void mclBnGT_add(mclBnGT *z, const mclBnGT *x, const mclBnGT *y);
void mclBnGT_sub(mclBnGT *z, const mclBnGT *x, const mclBnGT *y);
Square root of x
.
int mclBnFr_squareRoot(mclBnFr *y, const mclBnFr *x);
int mclBnFp_squareRoot(mclBnFp *y, const mclBnFp *x);
int mclBnFp2_squareRoot(mclBnFp2 *y, const mclBnFp2 *x);
y
is one of square root ofx
ify
exists.- return 0 if success else -1
add / sub / dbl / neg for G1
and G2
.
void mclBnG1_neg(mclBnG1 *y, const mclBnG1 *x);
void mclBnG1_dbl(mclBnG1 *y, const mclBnG1 *x);
void mclBnG1_add(mclBnG1 *z, const mclBnG1 *x, const mclBnG1 *y);
void mclBnG1_sub(mclBnG1 *z, const mclBnG1 *x, const mclBnG1 *y);
void mclBnG2_neg(mclBnG2 *y, const mclBnG2 *x);
void mclBnG2_dbl(mclBnG2 *y, const mclBnG2 *x);
void mclBnG2_add(mclBnG2 *z, const mclBnG2 *x, const mclBnG2 *y);
void mclBnG2_sub(mclBnG2 *z, const mclBnG2 *x, const mclBnG2 *y);
Convert a point from Jacobi coordinate to affine.
void mclBnG1_normalize(mclBnG1 *y, const mclBnG1 *x);
void mclBnG2_normalize(mclBnG2 *y, const mclBnG2 *x);
- convert
[x:y:z]
to[x:y:1]
ifz != 0
else[*:*:0]
scalar multiplication
void mclBnG1_mul(mclBnG1 *z, const mclBnG1 *x, const mclBnFr *y);
void mclBnG2_mul(mclBnG2 *z, const mclBnG2 *x, const mclBnFr *y);
void mclBnGT_pow(mclBnGT *z, const mclBnGT *x, const mclBnFr *y);
-
z = x * y for G1 / G2
-
z = pow(x, y) for GT
-
use
mclBnGT_powGeneric
for an element in Fp12 - GT.
multi scalar multiplication
void mclBnG1_mulVec(mclBnG1 *z, const mclBnG1 *x, const mclBnFr *y, mclSize n);
void mclBnG2_mulVec(mclBnG2 *z, const mclBnG2 *x, const mclBnFr *y, mclSize n);
void mclBnGT_powVec(mclBnGT *z, const mclBnGT *x, const mclBnFr *y, mclSize n);
- z = sum_{i=0}^{n-1} mul(x[i], y[i]) for G1 / G2.
- z = prod_{i=0}^{n-1} pow(x[i], y[i]) for GT.
hash and mapTo functions
Set hash of buf[0..bufSize-1]
to x
int mclBnFr_setHashOf(mclBnFr *x, const void *buf, mclSize bufSize);
int mclBnFp_setHashOf(mclBnFp *x, const void *buf, mclSize bufSize);
- always return 0
- use SHA-256 if sizeof(*x) <= 256 else SHA-512
- set accoring to the same way as
setLittleEndian
- support the other wasy if you want in the future
map x
to G1 / G2.
int mclBnFp_mapToG1(mclBnG1 *y, const mclBnFp *x);
int mclBnFp2_mapToG2(mclBnG2 *y, const mclBnFp2 *x);
- See
struct MapTo
inmcl/bn.hpp
for the detail of the algorithm. - return 0 if success else -1
hash and map to G1 / G2.
int mclBnG1_hashAndMapTo(mclBnG1 *x, const void *buf, mclSize bufSize);
int mclBnG2_hashAndMapTo(mclBnG2 *x, const void *buf, mclSize bufSize);
- Combine
setHashOf
andmapTo
functions
Pairing operations
The pairing function e(P, Q)
is consist of two parts:
MillerLoop(P, Q)
finalExp(x)
finalExp
satisfies the following properties:
e(P, Q) = finalExp(MillerLoop(P, Q))
e(P1, Q1) e(P2, Q2) = finalExp(MillerLoop(P1, Q1) MillerLoop(P2, Q2))
pairing
void mclBn_pairing(mclBnGT *z, const mclBnG1 *x, const mclBnG2 *y);
millerLoop
void mclBn_millerLoop(mclBnGT *z, const mclBnG1 *x, const mclBnG2 *y);
finalExp
void mclBn_finalExp(mclBnGT *y, const mclBnGT *x);
Variants of MillerLoop
multi pairing
void mclBn_millerLoopVec(mclBnGT *z, const mclBnG1 *x, const mclBnG2 *y, mclSize n);
- This function is for multi-pairing
- computes prod_{i=0}^{n-1} MillerLoop(x[i], y[i])
- prod_{i=0}^{n-1} e(x[i], y[i]) = finalExp(prod_{i=0}^{n-1} MillerLoop(x[i], y[i]))
pairing for a fixed point of G2
int mclBn_getUint64NumToPrecompute(void);
void mclBn_precomputeG2(uint64_t *Qbuf, const mclBnG2 *Q);
void mclBn_precomputedMillerLoop(mclBnGT *f, const mclBnG1 *P, const uint64_t *Qbuf);
These functions is the same computation of pairing(P, Q);
as the followings:
uint64_t *Qbuf = (uint64_t*)malloc(mclBn_getUint64NumToPrecompute() * sizeof(uint64_t));
mclBn_precomputeG2(Qbuf, Q); // precomputing of Q
mclBn_precomputedMillerLoop(f, P, Qbuf); // pairing of any P of G1 and the fixed Q
free(p);
void mclBn_precomputedMillerLoop2(
mclBnGT *f,
const mclBnG1 *P1, const uint64_t *Q1buf,
const mclBnG1 *P2, const uint64_t *Q2buf
);
- compute
MillerLoop(P1, Q1buf) * MillerLoop(P2, Q2buf)
void mclBn_precomputedMillerLoop2mixed(
mclBnGT *f,
const mclBnG1 *P1, const mclBnG2 *Q1,
const mclBnG1 *P2, const uint64_t *Q2buf
);
- compute
MillerLoop(P1, Q2) * MillerLoop(P2, Q2buf)
Check value
Check validness
int mclBnFr_isValid(const mclBnFr *x);
int mclBnFp_isValid(const mclBnFp *x);
int mclBnG1_isValid(const mclBnG1 *x);
int mclBnG2_isValid(const mclBnG2 *x);
- return 1 if true else 0
Check the order of a point
int mclBnG1_isValidOrder(const mclBnG1 *x);
int mclBnG2_isValidOrder(const mclBnG2 *x);
- Check whether the order of
x
is valid or not - return 1 if true else 0
- This function always cheks according to
mclBn_verifyOrderG1
andmclBn_verifyOrderG2
.
Is equal / zero / one / isOdd
int mclBnFr_isEqual(const mclBnFr *x, const mclBnFr *y);
int mclBnFr_isZero(const mclBnFr *x);
int mclBnFr_isOne(const mclBnFr *x);
int mclBnFr_isOdd(const mclBnFr *x);
int mclBnFp_isEqual(const mclBnFp *x, const mclBnFp *y);
int mclBnFp_isZero(const mclBnFp *x);
int mclBnFp_isOne(const mclBnFp *x);
int mclBnFp_isOdd(const mclBnFp *x);
int mclBnFp2_isEqual(const mclBnFp2 *x, const mclBnFp2 *y);
int mclBnFp2_isZero(const mclBnFp2 *x);
int mclBnFp2_isOne(const mclBnFp2 *x);
int mclBnG1_isEqual(const mclBnG1 *x, const mclBnG1 *y);
int mclBnG1_isZero(const mclBnG1 *x);
int mclBnG2_isEqual(const mclBnG2 *x, const mclBnG2 *y);
int mclBnG2_isZero(const mclBnG2 *x);
int mclBnGT_isEqual(const mclBnGT *x, const mclBnGT *y);
int mclBnGT_isZero(const mclBnGT *x);
int mclBnGT_isOne(const mclBnGT *x);
- return 1 if true else 0
isNegative
int mclBnFr_isNegative(const mclBnFr *x);
int mclBnFp_isNegative(const mclBnFr *x);
return 1 if x >= half where half = (r + 1) / 2 (resp. (p + 1) / 2).
Lagrange interpolation
int mclBn_FrLagrangeInterpolation(mclBnFr *out, const mclBnFr *xVec, const mclBnFr *yVec, mclSize k);
int mclBn_G1LagrangeInterpolation(mclBnG1 *out, const mclBnFr *xVec, const mclBnG1 *yVec, mclSize k);
int mclBn_G2LagrangeInterpolation(mclBnG2 *out, const mclBnFr *xVec, const mclBnG2 *yVec, mclSize k);
- Lagrange interpolation
- recover out = y(0) from {(xVec[i], yVec[i])} for {i=0..k-1}
- return 0 if success else -1
- satisfy that xVec[i] != 0, xVec[i] != xVec[j] for i != j
int mclBn_FrEvaluatePolynomial(mclBnFr *out, const mclBnFr *cVec, mclSize cSize, const mclBnFr *x);
int mclBn_G1EvaluatePolynomial(mclBnG1 *out, const mclBnG1 *cVec, mclSize cSize, const mclBnFr *x);
int mclBn_G2EvaluatePolynomial(mclBnG2 *out, const mclBnG2 *cVec, mclSize cSize, const mclBnFr *x);
- Evaluate polynomial
- out = f(x) = c[0] + c[1] * x + ... + c[cSize - 1] * x^{cSize - 1}
- return 0 if success else -1
- satisfy cSize >= 1