EpidStatus EpidSignBasic(MemberCtx const* ctx, void const* msg, size_t msg_len,
void const* basename, size_t basename_len,
BasicSignature* sig, BigNumStr* rnd_bsn) {
EpidStatus sts = kEpidErr;
EcPoint* B = NULL;
EcPoint* t = NULL; // temp value in G1
EcPoint* k = NULL;
EcPoint* e = NULL;
FfElement* R2 = NULL;
FfElement* p2y = NULL;
FfElement* t1 = NULL;
FfElement* t2 = NULL;
FfElement* a = NULL;
FfElement* b = NULL;
FfElement* rx = NULL;
FfElement* ra = NULL;
FfElement* rb = NULL;
struct p2x_t {
uint32_t i;
uint8_t bsn[1];
}* p2x = NULL;
FfElement* t3 = NULL; // temporary for multiplication
FfElement* c = NULL;
uint8_t* digest = NULL;
PreComputedSignature curr_presig = {0};
if (!ctx || !sig) {
return kEpidBadArgErr;
}
if (!msg && (0 != msg_len)) {
// if message is non-empty it must have both length and content
return kEpidBadArgErr;
}
if (!basename && (0 != basename_len)) {
// if basename is non-empty it must have both length and content
return kEpidBadArgErr;
}
if (!ctx->epid2_params) {
return kEpidBadArgErr;
}
do {
FiniteField* Fp = ctx->epid2_params->Fp;
SignCommitOutput commit_out = {0};
FpElemStr c_str = {0};
EcGroup* G1 = ctx->epid2_params->G1;
FiniteField* GT = ctx->epid2_params->GT;
FiniteField* Fq = ctx->epid2_params->Fq;
PairingState* ps_ctx = ctx->epid2_params->pairing_state;
const BigNumStr kOne = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1};
BigNumStr t1_str = {0};
BigNumStr t2_str = {0};
size_t digest_size = 0;
uint16_t* rf_ctr = (uint16_t*)&ctx->rf_ctr;
FfElement const* x = ctx->x;
if (basename) {
if (!IsBasenameAllowed(ctx->allowed_basenames, basename, basename_len)) {
sts = kEpidBadArgErr;
BREAK_ON_EPID_ERROR(sts);
}
}
sts = NewEcPoint(G1, &B);
BREAK_ON_EPID_ERROR(sts);
sts = NewEcPoint(G1, &k);
BREAK_ON_EPID_ERROR(sts);
sts = NewEcPoint(G1, &t);
BREAK_ON_EPID_ERROR(sts);
sts = NewEcPoint(G1, &e);
BREAK_ON_EPID_ERROR(sts);
sts = NewFfElement(GT, &R2);
BREAK_ON_EPID_ERROR(sts);
sts = NewFfElement(Fq, &p2y);
BREAK_ON_EPID_ERROR(sts);
sts = NewFfElement(Fp, &t1);
BREAK_ON_EPID_ERROR(sts);
sts = NewFfElement(Fp, &t2);
BREAK_ON_EPID_ERROR(sts);
p2x = (struct p2x_t*)SAFE_ALLOC(sizeof(struct p2x_t) + basename_len - 1);
if (!p2x) {
sts = kEpidMemAllocErr;
break;
}
sts = NewFfElement(Fp, &a);
BREAK_ON_EPID_ERROR(sts);
sts = NewFfElement(Fp, &b);
BREAK_ON_EPID_ERROR(sts);
sts = NewFfElement(Fp, &rx);
BREAK_ON_EPID_ERROR(sts);
sts = NewFfElement(Fp, &ra);
BREAK_ON_EPID_ERROR(sts);
sts = NewFfElement(Fp, &rb);
BREAK_ON_EPID_ERROR(sts);
sts = MemberGetPreSig((MemberCtx*)ctx, &curr_presig);
BREAK_ON_EPID_ERROR(sts);
// 3. If the pre-computed signature pre-sigma exists, the member
// loads (B, K, T, a, b, rx, rf, ra, rb, R1, R2) from
// pre-sigma. Refer to Section 4.4 for the computation of
// these values.
sts = ReadFfElement(Fp, &curr_presig.a, sizeof(curr_presig.a), a);
BREAK_ON_EPID_ERROR(sts);
sts = ReadFfElement(Fp, &curr_presig.b, sizeof(curr_presig.b), b);
BREAK_ON_EPID_ERROR(sts);
sts = ReadFfElement(Fp, &curr_presig.rx, sizeof(curr_presig.rx), rx);
BREAK_ON_EPID_ERROR(sts);
sts = ReadFfElement(Fp, &curr_presig.ra, sizeof(curr_presig.ra), ra);
BREAK_ON_EPID_ERROR(sts);
sts = ReadFfElement(Fp, &curr_presig.rb, sizeof(curr_presig.rb), rb);
BREAK_ON_EPID_ERROR(sts);
// If the basename is provided, use it, otherwise use presig B
if (basename) {
// 3.a. The member computes (B, i2, y2) = G1.tpmHash(bsn).
sts = EcHash(G1, basename, basename_len, ctx->hash_alg, B, &p2x->i);
BREAK_ON_EPID_ERROR(sts);
p2x->i = htonl(p2x->i);
sts = WriteEcPoint(G1, B, &commit_out.B, sizeof(commit_out.B));
BREAK_ON_EPID_ERROR(sts);
sts = ReadFfElement(Fq, &commit_out.B.y, sizeof(commit_out.B.y), p2y);
BREAK_ON_EPID_ERROR(sts);
// b.i. (KTPM, LTPM, ETPM, counterTPM) = TPM2_Commit(P1=h1,(s2, y2) = (i2
// || bsn, y2)).
// b.ii.K = KTPM.
if (0 !=
memcpy_S((void*)p2x->bsn, basename_len, basename, basename_len)) {
sts = kEpidBadArgErr;
break;
}
sts =
Tpm2Commit(ctx->tpm2_ctx, ctx->h1, p2x, sizeof(p2x->i) + basename_len,
p2y, k, t, e, (uint16_t*)&ctx->rf_ctr);
BREAK_ON_EPID_ERROR(sts);
sts = WriteEcPoint(G1, k, &commit_out.K, sizeof(commit_out.K));
BREAK_ON_EPID_ERROR(sts);
// c.i. The member computes R1 = LTPM.
sts = WriteEcPoint(G1, t, &commit_out.R1, sizeof(commit_out.R1));
BREAK_ON_EPID_ERROR(sts);
// c.ii. e12rf = pairing(ETPM, g2)
sts = Pairing(ps_ctx, e, ctx->epid2_params->g2, R2);
BREAK_ON_EPID_ERROR(sts);
// c.iii. R2 = GT.sscmMultiExp(ea2, t1, e12rf, 1, e22, t2, e2w,ra).
// 4.i. The member computes t1 = (- rx) mod p.
sts = FfNeg(Fp, rx, t1);
BREAK_ON_EPID_ERROR(sts);
// 4.j. The member computes t2 = (rb - a * rx) mod p.
sts = FfMul(Fp, a, rx, t2);
BREAK_ON_EPID_ERROR(sts);
sts = FfNeg(Fp, t2, t2);
BREAK_ON_EPID_ERROR(sts);
sts = FfAdd(Fp, rb, t2, t2);
BREAK_ON_EPID_ERROR(sts);
sts = WriteFfElement(Fp, t1, &t1_str, sizeof(t1_str));
BREAK_ON_EPID_ERROR(sts);
sts = WriteFfElement(Fp, t2, &t2_str, sizeof(t2_str));
BREAK_ON_EPID_ERROR(sts);
{
FfElement const* points[4];
BigNumStr const* exponents[4];
points[0] = ctx->ea2;
points[1] = R2;
points[2] = ctx->e22;
points[3] = ctx->e2w;
exponents[0] = &t1_str;
exponents[1] = &kOne;
exponents[2] = &t2_str;
exponents[3] = (BigNumStr*)&curr_presig.ra;
sts = FfMultiExp(GT, points, exponents, COUNT_OF(points), R2);
BREAK_ON_EPID_ERROR(sts);
}
sts = WriteFfElement(GT, R2, &commit_out.R2, sizeof(commit_out.R2));
BREAK_ON_EPID_ERROR(sts);
// d. The member over-writes the counterTPM, B, K, R1 and R2 values.
} else {
if (!rnd_bsn) {
sts = kEpidBadArgErr;
break;
}
sts = ReadEcPoint(G1, &curr_presig.B, sizeof(curr_presig.B), B);
BREAK_ON_EPID_ERROR(sts);
commit_out.B = curr_presig.B;
commit_out.K = curr_presig.K;
commit_out.R1 = curr_presig.R1;
((MemberCtx*)ctx)->rf_ctr = curr_presig.rf_ctr;
commit_out.R2 = curr_presig.R2;
*rnd_bsn = curr_presig.rnd_bsn;
}
commit_out.T = curr_presig.T;
sts = HashSignCommitment(Fp, ctx->hash_alg, &ctx->pub_key, &commit_out, msg,
msg_len, &c_str);
BREAK_ON_EPID_ERROR(sts);
digest_size = EpidGetHashSize(ctx->hash_alg);
digest = (uint8_t*)SAFE_ALLOC(digest_size);
if (!digest) {
sts = kEpidNoMemErr;
break;
}
memcpy_S(digest + digest_size - sizeof(c_str), sizeof(c_str), &c_str,
sizeof(c_str));
sts = NewFfElement(Fp, &t3);
BREAK_ON_EPID_ERROR(sts);
sts = NewFfElement(Fp, &c);
BREAK_ON_EPID_ERROR(sts);
sts = ReadFfElement(Fp, &c_str, sizeof(c_str), c);
BREAK_ON_EPID_ERROR(sts);
// 7. The member computes sx = (rx + c * x) mod p.
sts = FfMul(Fp, c, x, t3);
BREAK_ON_EPID_ERROR(sts);
sts = FfAdd(Fp, rx, t3, t3);
BREAK_ON_EPID_ERROR(sts);
sts = WriteFfElement(Fp, t3, &sig->sx, sizeof(sig->sx));
BREAK_ON_EPID_ERROR(sts);
// 8. The member computes sf = (rf + c * f) mod p.
sts = Tpm2Sign(ctx->tpm2_ctx, digest, digest_size, *rf_ctr, NULL, t3);
BREAK_ON_EPID_ERROR(sts);
sts = WriteFfElement(Fp, t3, &sig->sf, sizeof(sig->sf));
BREAK_ON_EPID_ERROR(sts);
// 9. The member computes sa = (ra + c * a) mod p.
sts = FfMul(Fp, c, a, t3);
BREAK_ON_EPID_ERROR(sts);
sts = FfAdd(Fp, ra, t3, t3);
BREAK_ON_EPID_ERROR(sts);
sts = WriteFfElement(Fp, t3, &sig->sa, sizeof(sig->sa));
BREAK_ON_EPID_ERROR(sts);
// 10. The member computes sb = (rb + c * b) mod p.
sts = FfMul(Fp, c, b, t3);
BREAK_ON_EPID_ERROR(sts);
sts = FfAdd(Fp, rb, t3, t3);
BREAK_ON_EPID_ERROR(sts);
sts = WriteFfElement(Fp, t3, &sig->sb, sizeof(sig->sb));
BREAK_ON_EPID_ERROR(sts);
sig->B = commit_out.B;
sig->K = commit_out.K;
sig->T = commit_out.T;
sig->c = c_str;
sts = kEpidNoErr;
} while (0);
if (sts != kEpidNoErr) {
(void)Tpm2ReleaseCounter(ctx->tpm2_ctx, (uint16_t)ctx->rf_ctr);
(void)Tpm2ReleaseCounter(ctx->tpm2_ctx, curr_presig.rf_ctr);
} else if (basename) {
(void)Tpm2ReleaseCounter(ctx->tpm2_ctx, curr_presig.rf_ctr);
}
EpidZeroMemory(&curr_presig, sizeof(curr_presig));
DeleteEcPoint(&B);
DeleteEcPoint(&k);
DeleteEcPoint(&t);
DeleteEcPoint(&e);
DeleteFfElement(&R2);
DeleteFfElement(&p2y);
DeleteFfElement(&t1);
DeleteFfElement(&t2);
DeleteFfElement(&a);
DeleteFfElement(&b);
DeleteFfElement(&rx);
DeleteFfElement(&ra);
DeleteFfElement(&rb);
SAFE_FREE(p2x);
DeleteFfElement(&t3);
DeleteFfElement(&c);
SAFE_FREE(digest);
return sts;
}
EpidStatus EpidComputePreSig(MemberCtx const* ctx,
PreComputedSignature* precompsig) {
EpidStatus res = kEpidNotImpl;
EcPoint* B = NULL;
EcPoint* K = NULL;
EcPoint* T = NULL;
EcPoint* R1 = NULL;
FfElement* R2 = NULL;
FfElement* a = NULL;
FfElement* b = NULL;
FfElement* rx = NULL;
FfElement* rf = NULL;
FfElement* ra = NULL;
FfElement* rb = NULL;
FfElement* t1 = NULL;
FfElement* t2 = NULL;
FfElement* f = NULL;
if (!ctx || !precompsig) return kEpidBadArgErr;
if (!ctx->epid2_params || !ctx->pub_key || !ctx->priv_key)
return kEpidBadArgErr;
do {
// handy shorthands:
EcGroup* G1 = ctx->epid2_params->G1;
FiniteField* GT = ctx->epid2_params->GT;
FiniteField* Fp = ctx->epid2_params->Fp;
EcPoint* h2 = ctx->pub_key->h2;
EcPoint* A = ctx->priv_key->A;
FfElement* x = ctx->priv_key->x;
BigNumStr f_str = {0};
BigNumStr a_str = {0};
BigNumStr t1_str = {0};
BigNumStr rf_str = {0};
BigNumStr t2_str = {0};
BigNumStr ra_str = {0};
static const BigNumStr one = {
{{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}}};
if (!G1 || !GT || !Fp || !h2 || !A || !x || !ctx->priv_key->f ||
!ctx->e12 || !ctx->e22 || !ctx->e2w || !ctx->ea2) {
res = kEpidBadArgErr;
BREAK_ON_EPID_ERROR(res);
}
f = ctx->priv_key->f;
// The following variables B, K, T, R1 (elements of G1), R2
// (elements of GT), a, b, rx, rf, ra, rb, t1, t2 (256-bit
// integers) are used.
res = NewEcPoint(G1, &B);
BREAK_ON_EPID_ERROR(res);
res = NewEcPoint(G1, &K);
BREAK_ON_EPID_ERROR(res);
res = NewEcPoint(G1, &T);
BREAK_ON_EPID_ERROR(res);
res = NewEcPoint(G1, &R1);
BREAK_ON_EPID_ERROR(res);
res = NewFfElement(GT, &R2);
BREAK_ON_EPID_ERROR(res);
res = NewFfElement(Fp, &a);
BREAK_ON_EPID_ERROR(res);
res = NewFfElement(Fp, &b);
BREAK_ON_EPID_ERROR(res);
res = NewFfElement(Fp, &rx);
BREAK_ON_EPID_ERROR(res);
res = NewFfElement(Fp, &rf);
BREAK_ON_EPID_ERROR(res);
res = NewFfElement(Fp, &ra);
BREAK_ON_EPID_ERROR(res);
res = NewFfElement(Fp, &rb);
BREAK_ON_EPID_ERROR(res);
res = NewFfElement(Fp, &t1);
BREAK_ON_EPID_ERROR(res);
res = NewFfElement(Fp, &t2);
BREAK_ON_EPID_ERROR(res);
// 1. The member expects the pre-computation is done (e12, e22, e2w,
// ea2). Refer to Section 3.5 for the computation of these
// values.
// 2. The member verifies gid in public key matches gid in private
// key.
// 3. The member computes B = G1.getRandom().
res = EcGetRandom(G1, ctx->rnd_func, ctx->rnd_param, B);
BREAK_ON_EPID_ERROR(res);
// 4. The member computes K = G1.sscmExp(B, f).
res = WriteFfElement(Fp, f, &f_str, sizeof(f_str));
BREAK_ON_EPID_ERROR(res);
res = EcExp(G1, B, &f_str, K);
BREAK_ON_EPID_ERROR(res);
// 5. The member chooses randomly an integers a from [1, p-1].
res = FfGetRandom(Fp, &one, ctx->rnd_func, ctx->rnd_param, a);
BREAK_ON_EPID_ERROR(res);
// 6. The member computes T = G1.sscmExp(h2, a).
res = WriteFfElement(Fp, a, &a_str, sizeof(a_str));
BREAK_ON_EPID_ERROR(res);
res = EcExp(G1, h2, &a_str, T);
BREAK_ON_EPID_ERROR(res);
// 7. The member computes T = G1.mul(T, A).
res = EcMul(G1, T, A, T);
BREAK_ON_EPID_ERROR(res);
// 8. The member computes b = (a * x) mod p.
res = FfMul(Fp, a, x, b);
BREAK_ON_EPID_ERROR(res);
// 9. The member chooses rx, rf, ra, rb randomly from [1, p-1].
res = FfGetRandom(Fp, &one, ctx->rnd_func, ctx->rnd_param, rx);
BREAK_ON_EPID_ERROR(res);
res = FfGetRandom(Fp, &one, ctx->rnd_func, ctx->rnd_param, rf);
BREAK_ON_EPID_ERROR(res);
res = FfGetRandom(Fp, &one, ctx->rnd_func, ctx->rnd_param, ra);
BREAK_ON_EPID_ERROR(res);
res = FfGetRandom(Fp, &one, ctx->rnd_func, ctx->rnd_param, rb);
BREAK_ON_EPID_ERROR(res);
// 10. The member computes t1 = (- rx) mod p.
res = FfNeg(Fp, rx, t1);
BREAK_ON_EPID_ERROR(res);
// 11. The member computes t2 = (rb - a * rx) mod p.
res = FfMul(Fp, a, rx, t2);
BREAK_ON_EPID_ERROR(res);
res = FfNeg(Fp, t2, t2);
BREAK_ON_EPID_ERROR(res);
res = FfAdd(Fp, rb, t2, t2);
BREAK_ON_EPID_ERROR(res);
// 12. The member computes R1 = G1.sscmExp(B, rf).
res = WriteFfElement(Fp, rf, &rf_str, sizeof(rf_str));
BREAK_ON_EPID_ERROR(res);
res = EcExp(G1, B, &rf_str, R1);
BREAK_ON_EPID_ERROR(res);
// 13. The member computes R2 = GT.sscmMultiExp(ea2, t1, e12, rf,
// e22, t2, e2w, ra).
res = WriteFfElement(Fp, t1, &t1_str, sizeof(t1_str));
BREAK_ON_EPID_ERROR(res);
res = WriteFfElement(Fp, t2, &t2_str, sizeof(t2_str));
BREAK_ON_EPID_ERROR(res);
res = WriteFfElement(Fp, ra, &ra_str, sizeof(ra_str));
BREAK_ON_EPID_ERROR(res);
{
FfElement const* points[4];
BigNumStr const* exponents[4];
points[0] = ctx->ea2;
points[1] = ctx->e12;
points[2] = ctx->e22;
points[3] = ctx->e2w;
exponents[0] = &t1_str;
exponents[1] = &rf_str;
exponents[2] = &t2_str;
exponents[3] = &ra_str;
res = FfMultiExp(GT, points, exponents, COUNT_OF(points), R2);
BREAK_ON_EPID_ERROR(res);
}
// 14. The member sets and outputs pre-sigma = (B, K, T, a, b, rx,
// rf, ra, rb, R1, R2).
res = WriteEcPoint(G1, B, &precompsig->B, sizeof(precompsig->B));
BREAK_ON_EPID_ERROR(res);
res = WriteEcPoint(G1, K, &precompsig->K, sizeof(precompsig->K));
BREAK_ON_EPID_ERROR(res);
res = WriteEcPoint(G1, T, &precompsig->T, sizeof(precompsig->T));
BREAK_ON_EPID_ERROR(res);
res = WriteFfElement(Fp, a, &precompsig->a, sizeof(precompsig->a));
BREAK_ON_EPID_ERROR(res);
res = WriteFfElement(Fp, b, &precompsig->b, sizeof(precompsig->b));
BREAK_ON_EPID_ERROR(res);
res = WriteFfElement(Fp, rx, &precompsig->rx, sizeof(precompsig->rx));
BREAK_ON_EPID_ERROR(res);
res = WriteFfElement(Fp, rf, &precompsig->rf, sizeof(precompsig->rf));
BREAK_ON_EPID_ERROR(res);
res = WriteFfElement(Fp, ra, &precompsig->ra, sizeof(precompsig->ra));
BREAK_ON_EPID_ERROR(res);
res = WriteFfElement(Fp, rb, &precompsig->rb, sizeof(precompsig->rb));
BREAK_ON_EPID_ERROR(res);
res = WriteEcPoint(G1, R1, &precompsig->R1, sizeof(precompsig->R1));
BREAK_ON_EPID_ERROR(res);
res = WriteFfElement(GT, R2, &precompsig->R2, sizeof(precompsig->R2));
BREAK_ON_EPID_ERROR(res);
// 15. The member stores pre-sigma in the secure storage of the
// member.
res = kEpidNoErr;
} while (0);
f = NULL;
DeleteEcPoint(&B);
DeleteEcPoint(&K);
DeleteEcPoint(&T);
DeleteEcPoint(&R1);
DeleteFfElement(&R2);
DeleteFfElement(&a);
DeleteFfElement(&b);
DeleteFfElement(&rx);
DeleteFfElement(&rf);
DeleteFfElement(&ra);
DeleteFfElement(&rb);
DeleteFfElement(&t1);
DeleteFfElement(&t2);
return (res);
}
