EpidStatus EpidCheckPrivRlEntry(VerifierCtx const* ctx,
BasicSignature const* sig, FpElemStr const* f) {
EpidStatus result = kEpidErr;
EcPoint* b = NULL;
EcPoint* k = NULL;
EcPoint* t4 = NULL;
EcGroup* G1 = NULL;
FfElement* ff_elem = NULL;
if (!ctx || !sig || !f) {
return kEpidBadArgErr;
}
if (!ctx->epid2_params || !ctx->epid2_params->G1) {
return kEpidBadArgErr;
}
do {
// Section 4.1.2 Step 4.b For i = 0, ... , n1-1, the verifier computes t4
// =G1.exp(B, f[i]) and verifies that G1.isEqual(t4, K) = false.
bool compare_result = false;
FiniteField* Fp = ctx->epid2_params->Fp;
G1 = ctx->epid2_params->G1;
result = NewFfElement(Fp, &ff_elem);
if (kEpidNoErr != result) {
break;
}
result = NewEcPoint(G1, &b);
if (kEpidNoErr != result) {
break;
}
result = NewEcPoint(G1, &k);
if (kEpidNoErr != result) {
break;
}
result = NewEcPoint(G1, &t4);
if (kEpidNoErr != result) {
break;
}
// ReadFfElement checks that the value f is in the field
result = ReadFfElement(Fp, (BigNumStr const*)f, sizeof(BigNumStr), ff_elem);
if (kEpidNoErr != result) {
break;
}
result = ReadEcPoint(G1, &sig->B, sizeof(sig->B), b);
if (kEpidNoErr != result) {
break;
}
result = ReadEcPoint(G1, &sig->K, sizeof(sig->K), k);
if (kEpidNoErr != result) {
break;
}
result = EcExp(G1, b, (BigNumStr const*)f, t4);
if (kEpidNoErr != result) {
break;
}
result = EcIsEqual(G1, t4, k, &compare_result);
if (kEpidNoErr != result) {
break;
}
// if t4 == k, sig revoked in PrivRl
if (compare_result) {
result = kEpidSigRevokedInPrivRl;
} else {
result = kEpidNoErr;
}
} while (0);
DeleteFfElement(&ff_elem);
DeleteEcPoint(&t4);
DeleteEcPoint(&k);
DeleteEcPoint(&b);
return result;
}
EpidStatus EpidRequestJoin(GroupPubKey const* pub_key, IssuerNonce const* ni,
FpElemStr const* f, BitSupplier rnd_func,
void* rnd_param, HashAlg hash_alg,
JoinRequest* join_request) {
EpidStatus sts;
static const BigNumStr one = {
{{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}}};
BigNumStr r_str;
JoinPCommitValues commit_values;
Epid2Params_* params = NULL;
FfElement* r_el = NULL;
FfElement* f_el = NULL;
FfElement* c_el = NULL;
FfElement* cf_el = NULL;
FfElement* s_el = NULL;
EcPoint* f_pt = NULL;
EcPoint* r_pt = NULL;
EcPoint* h1_pt = NULL;
if (!pub_key || !ni || !f || !rnd_func || !join_request) {
return kEpidBadArgErr;
}
if (kSha256 != hash_alg && kSha384 != hash_alg && kSha512 != hash_alg) {
return kEpidBadArgErr;
}
do {
sts = CreateEpid2Params(¶ms);
BREAK_ON_EPID_ERROR(sts);
if (!params->Fp || !params->G1) {
sts = kEpidBadArgErr;
break;
}
sts = NewFfElement(params->Fp, &r_el);
BREAK_ON_EPID_ERROR(sts);
sts = NewFfElement(params->Fp, &f_el);
BREAK_ON_EPID_ERROR(sts);
sts = NewFfElement(params->Fp, &c_el);
BREAK_ON_EPID_ERROR(sts);
sts = NewFfElement(params->Fp, &cf_el);
BREAK_ON_EPID_ERROR(sts);
sts = NewFfElement(params->Fp, &s_el);
BREAK_ON_EPID_ERROR(sts);
sts = NewEcPoint(params->G1, &f_pt);
BREAK_ON_EPID_ERROR(sts);
sts = NewEcPoint(params->G1, &h1_pt);
BREAK_ON_EPID_ERROR(sts);
sts = NewEcPoint(params->G1, &r_pt);
BREAK_ON_EPID_ERROR(sts);
sts = ReadFfElement(params->Fp, (uint8_t const*)f, sizeof(*f), f_el);
BREAK_ON_EPID_ERROR(sts);
sts = ReadEcPoint(params->G1, (uint8_t*)&pub_key->h1, sizeof(pub_key->h1),
h1_pt);
BREAK_ON_EPID_ERROR(sts);
// Step 1. The member chooses a random integer r from [1, p-1].
sts = FfGetRandom(params->Fp, &one, rnd_func, rnd_param, r_el);
BREAK_ON_EPID_ERROR(sts);
sts = WriteFfElement(params->Fp, r_el, (uint8_t*)&r_str, sizeof(r_str));
// Step 2. The member computes F = G1.sscmExp(h1, f).
sts = EcExp(params->G1, h1_pt, (BigNumStr const*)f, f_pt);
BREAK_ON_EPID_ERROR(sts);
// Step 3. The member computes R = G1.sscmExp(h1, r).
sts = EcExp(params->G1, h1_pt, (BigNumStr const*)&r_str, r_pt);
BREAK_ON_EPID_ERROR(sts);
// Step 4. The member computes c = Fp.hash(p || g1 || g2 || h1 || h2 || w ||
// F || R || NI). Refer to Section 7.1 for hash operation over a prime
// field.
sts = WriteBigNum(params->p, sizeof(commit_values.p),
(uint8_t*)&commit_values.p);
BREAK_ON_EPID_ERROR(sts);
sts = WriteEcPoint(params->G1, params->g1, (uint8_t*)&commit_values.g1,
sizeof(commit_values.g1));
BREAK_ON_EPID_ERROR(sts);
sts = WriteEcPoint(params->G2, params->g2, (uint8_t*)&commit_values.g2,
sizeof(commit_values.g2));
BREAK_ON_EPID_ERROR(sts);
commit_values.h1 = pub_key->h1;
commit_values.h2 = pub_key->h2;
commit_values.w = pub_key->w;
sts = WriteEcPoint(params->G1, f_pt, (uint8_t*)&commit_values.F,
sizeof(commit_values.F));
BREAK_ON_EPID_ERROR(sts);
sts = WriteEcPoint(params->G1, r_pt, (uint8_t*)&commit_values.R,
sizeof(commit_values.R));
BREAK_ON_EPID_ERROR(sts);
commit_values.NI = *ni;
sts = FfHash(params->Fp, (uint8_t*)&commit_values, sizeof(commit_values),
hash_alg, c_el);
BREAK_ON_EPID_ERROR(sts);
// Step 5. The member computes s = (r + c * f) mod p.
sts = FfMul(params->Fp, c_el, f_el, cf_el);
BREAK_ON_EPID_ERROR(sts);
sts = FfAdd(params->Fp, r_el, cf_el, s_el);
BREAK_ON_EPID_ERROR(sts);
// Step 6. The output join request is (F, c, s).
sts = WriteFfElement(params->Fp, c_el, (uint8_t*)&join_request->c,
sizeof(join_request->c));
BREAK_ON_EPID_ERROR(sts);
sts = WriteFfElement(params->Fp, s_el, (uint8_t*)&join_request->s,
sizeof(join_request->s));
BREAK_ON_EPID_ERROR(sts);
sts = WriteEcPoint(params->G1, f_pt, (uint8_t*)&join_request->F,
sizeof(join_request->F));
BREAK_ON_EPID_ERROR(sts);
sts = kEpidNoErr;
} while (0);
DeleteEcPoint(&h1_pt);
DeleteEcPoint(&r_pt);
DeleteEcPoint(&f_pt);
DeleteFfElement(&s_el);
DeleteFfElement(&cf_el);
DeleteFfElement(&c_el);
DeleteFfElement(&f_el);
DeleteFfElement(&r_el);
DeleteEpid2Params(¶ms);
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);
}
EpidStatus Tpm2LoadExternal(Tpm2Ctx* ctx, FpElemStr const* f_str) {
EpidStatus sts = kEpidErr;
TPM_RC rc = TPM_RC_SUCCESS;
EcPoint* pub = NULL;
FfElement* f = NULL;
TPMI_ALG_HASH tpm_hash_alg = TPM_ALG_NULL;
if (!ctx || !ctx->epid2_params || !f_str) {
return kEpidBadArgErr;
}
do {
LoadExternal_In in = {0};
LoadExternal_Out out;
G1ElemStr pub_str = {0};
TPMS_ECC_PARMS* ecc_details = &in.inPublic.publicArea.parameters.eccDetail;
EcGroup* G1 = ctx->epid2_params->G1;
EcPoint* g1 = ctx->epid2_params->g1;
sts = NewFfElement(ctx->epid2_params->Fp, &f);
BREAK_ON_EPID_ERROR(sts);
// verify that f is valid
sts = ReadFfElement(ctx->epid2_params->Fp, f_str, sizeof(*f_str), f);
BREAK_ON_EPID_ERROR(sts);
if (ctx->key_handle) {
FlushContext_In in_fc;
in_fc.flushHandle = ctx->key_handle;
TSS_Execute(ctx->tss, NULL, (COMMAND_PARAMETERS*)&in_fc, NULL,
TPM_CC_FlushContext, TPM_RH_NULL, NULL, 0);
if (rc != TPM_RC_SUCCESS) {
print_tpm2_response_code("TPM2_FlushContext", rc);
}
ctx->key_handle = 0;
}
sts = NewEcPoint(G1, &pub);
BREAK_ON_EPID_ERROR(sts);
sts = EcExp(G1, g1, (BigNumStr const*)f_str, pub);
BREAK_ON_EPID_ERROR(sts);
sts = WriteEcPoint(G1, pub, &pub_str, sizeof(pub_str));
BREAK_ON_EPID_ERROR(sts);
tpm_hash_alg = EpidtoTpm2HashAlg(ctx->hash_alg);
if (tpm_hash_alg == TPM_ALG_NULL) {
sts = kEpidHashAlgorithmNotSupported;
break;
}
in.hierarchy = TPM_RH_NULL;
in.inPublic.size = sizeof(TPM2B_PUBLIC);
in.inPublic.publicArea.type = TPM_ALG_ECC;
in.inPublic.publicArea.nameAlg = tpm_hash_alg;
in.inPublic.publicArea.objectAttributes.val =
TPMA_OBJECT_NODA | TPMA_OBJECT_USERWITHAUTH | TPMA_OBJECT_SIGN;
in.inPublic.publicArea.authPolicy.t.size = 0;
ecc_details->symmetric.algorithm = TPM_ALG_NULL;
ecc_details->scheme.scheme = TPM_ALG_ECDAA;
ecc_details->scheme.details.ecdaa.hashAlg = tpm_hash_alg;
ecc_details->scheme.details.ecdaa.count = 0;
ecc_details->curveID = TPM_ECC_BN_P256;
ecc_details->kdf.scheme = TPM_ALG_NULL;
sts = ReadTpm2FfElement(&pub_str.x.data,
&in.inPublic.publicArea.unique.ecc.x);
BREAK_ON_EPID_ERROR(sts);
sts = ReadTpm2FfElement(&pub_str.y.data,
&in.inPublic.publicArea.unique.ecc.y);
BREAK_ON_EPID_ERROR(sts);
in.inPrivate.t.size = sizeof(in.inPrivate.t.sensitiveArea);
in.inPrivate.t.sensitiveArea.sensitiveType = TPM_ALG_ECC;
sts = ReadTpm2FfElement(&f_str->data,
&in.inPrivate.t.sensitiveArea.sensitive.ecc);
BREAK_ON_EPID_ERROR(sts);
rc = TSS_Execute(ctx->tss, (RESPONSE_PARAMETERS*)&out,
(COMMAND_PARAMETERS*)&in, NULL, TPM_CC_LoadExternal,
TPM_RH_NULL, NULL, 0);
if (rc != TPM_RC_SUCCESS) {
print_tpm2_response_code("TPM2_LoadExternal", rc);
if (TPM_RC_BINDING == rc || TPM_RC_ECC_POINT == rc ||
TPM_RC_KEY_SIZE == rc)
sts = kEpidBadArgErr;
else
sts = kEpidErr;
break;
}
ctx->key_handle = out.objectHandle;
} while (0);
DeleteEcPoint(&pub);
DeleteFfElement(&f);
return sts;
}
