/// <summary>
/// Verifies a U-Prove token signature.
/// </summary>
/// <param name="ip">The Issuer parameters corresponding to the U-Prove token.</param>
/// <param name="upt">The U-Prove token to verify.</param>
/// <exception cref="InvalidUProveArtifactException">If the U-Prove token is invalid.</exception>
public static void VerifyTokenSignature(IssuerParameters ip, UProveToken upt)
{
Group Gq = ip.Gq;
FieldZq Zq = ip.Zq;
if (upt.H == Gq.Identity)
{
throw new InvalidUProveArtifactException("Invalid U-Prove token (public key H = 1)");
}
GroupElement[] bases = new GroupElement[2];
FieldZqElement[] exponents = new FieldZqElement[2];
HashFunction hash = ip.HashFunction;
hash.Hash(upt.H);
hash.Hash(upt.PI);
hash.Hash(upt.SigmaZPrime);
bases[0] = Gq.G; exponents[0] = upt.SigmaRPrime;
bases[1] = ip.G[0]; exponents[1] = upt.SigmaCPrime.Negate();
hash.Hash(Gq.MultiExponentiate(bases, exponents));
bases[0] = upt.H; exponents[0] = upt.SigmaRPrime;
bases[1] = upt.SigmaZPrime; exponents[1] = upt.SigmaCPrime.Negate();
hash.Hash(Gq.MultiExponentiate(bases, exponents));
if (upt.SigmaCPrime != Zq.GetElementFromDigest(hash.Digest))
{
throw new InvalidUProveArtifactException("Invalid U-Prove token signature");
}
}
/// <summary>
/// Generates the U-Prove key and tokens.
/// </summary>
/// <param name="message">The third issuance message.</param>
/// <param name="skipTokenValidation">Set to <code>true</code> to skip token validation;
/// <code>false</code> otherwise. Token validation SHOULD be performed before use, either
/// by setting <code>skipTokenValidation</code> to <code>false</code>, or by later using the
/// <code>ProtocolHelper.VerifyTokenSignature</code> method.
/// </param>
/// <exception cref="InvalidUProveArtifactException">If the token signature is invalid.</exception>
/// <returns>An array of U-Prove keys and tokens</returns>
public UProveKeyAndToken[] GenerateTokens(ThirdIssuanceMessage message, bool skipTokenValidation = false)
{
if (state != State.Second)
{
throw new InvalidOperationException("GenerateSecondMessage must be called first");
}
bool doBatchValidation = !skipTokenValidation && batchValidationSecurityLevel > 0;
bool doNormalValidation = !skipTokenValidation && batchValidationSecurityLevel <= 0;
Group Gq = ip.Gq;
FieldZq Zq = ip.Zq;
FieldZqElement[] sigmaRPrime = new FieldZqElement[numberOfTokens];
FieldZqElement phoAR = Zq.Zero, phoR = Zq.Zero, phoAC = Zq.Zero, phoC = Zq.Zero;
GroupElement[] batchAccBases = new GroupElement[numberOfTokens];
FieldZqElement[] s = null;
if (!skipTokenValidation)
{
s = Zq.GetRandomElements(numberOfTokens, true, batchValidationSecurityLevel);
}
for (int i = 0; i < numberOfTokens; i++)
{
sigmaRPrime[i] = message.sigmaR[i] + beta2[i];
if (doBatchValidation)
{
phoAR += (s[i] * alpha[i] * sigmaRPrime[i]);
phoR += (s[i] * sigmaRPrime[i]);
phoAC += (s[i] * alpha[i] * sigmaCPrime[i]);
phoC += (s[i] * sigmaCPrime[i]);
batchAccBases[i] = sigmaAPrime[i] * sigmaBPrime[i];
}
else if (doNormalValidation)
{
if (!(sigmaAPrime[i] * sigmaBPrime[i]).Equals(
Gq.MultiExponentiate(new GroupElement[] { Gq.G *h[i], ip.G[0] * sigmaZPrime[i] },
new FieldZqElement[] { sigmaRPrime[i], sigmaCPrime[i].Negate() })))
{
throw new InvalidUProveArtifactException("Invalid token signature: " + i);
}
}
ukat[i].Token = new UProveToken(ip.UidP, h[i], TI, PI, sigmaZPrime[i], sigmaCPrime[i], sigmaRPrime[i], isDeviceProtected);
}
if (doBatchValidation &&
(Gq.MultiExponentiate(batchAccBases, s) !=
Gq.MultiExponentiate(new GroupElement[] { Gq.G, gamma, ip.G[0], sigmaZ },
new FieldZqElement[] { phoR, phoAR, phoC.Negate(), phoAC.Negate() }))) // TODO: batch validation with blinded gamma needs to multiply beta0inverse to phoAR
{
throw new InvalidUProveArtifactException("Invalid token signature");
}
state = State.Tokens;
return(ukat);
}
/// <summary>
/// Generates the second issuance message.
/// </summary>
/// <param name="message">The first issuance message.</param>
/// <returns>The second issuance message.</returns>
public SecondIssuanceMessage GenerateSecondMessage(FirstIssuanceMessage message)
{
if (state != State.Initialized)
{
throw new InvalidOperationException("Prover not initialized properly");
}
Group Gq = ip.Gq;
this.sigmaZ = message.sigmaZ.Exponentiate(beta0Inverse); // remove the blind that was included in gamma (if no blind beta0Inverse = 1)
sigmaZPrime = new GroupElement[numberOfTokens];
sigmaAPrime = new GroupElement[numberOfTokens];
sigmaBPrime = new GroupElement[numberOfTokens];
sigmaCPrime = new FieldZqElement[numberOfTokens];
FieldZqElement[] sigmaC = new FieldZqElement[numberOfTokens];
for (int i = 0; i < numberOfTokens; i++)
{
FieldZqElement sigmaBExponent = alpha[i].Multiply(beta0Inverse); // will remove the collab-issuance blind, if present
sigmaZPrime[i] = this.sigmaZ.Exponentiate(alpha[i]);
sigmaAPrime[i] = t1[i] * message.sigmaA[i];
sigmaBPrime[i] = Gq.MultiExponentiate(new GroupElement[] { sigmaZPrime[i], h[i], message.sigmaB[i] }, new FieldZqElement[] { beta1[i], beta2[i], sigmaBExponent });
HashFunction hash = ip.HashFunction;
hash.Hash(h[i]);
hash.Hash(PI);
hash.Hash(sigmaZPrime[i]);
hash.Hash(sigmaAPrime[i]);
hash.Hash(sigmaBPrime[i]);
sigmaCPrime[i] = ip.Zq.GetElementFromDigest(hash.Digest);
sigmaC[i] = sigmaCPrime[i] + beta1[i];
}
state = State.Second;
return(new SecondIssuanceMessage(sigmaC));
}
private void Precompute(GroupElement gamma, ProverRandomData pregeneratedRandomData)
{
Group Gq = ip.Gq;
FieldZq Zq = ip.Zq;
if (pregeneratedRandomData == null)
{
alpha = Zq.GetRandomElements(numberOfTokens, true);
beta1 = Zq.GetRandomElements(numberOfTokens, false);
beta2 = Zq.GetRandomElements(numberOfTokens, false);
}
else
{
alpha = pregeneratedRandomData.Alpha;
beta1 = pregeneratedRandomData.Beta1;
beta2 = pregeneratedRandomData.Beta2;
}
h = new GroupElement[numberOfTokens];
t1 = new GroupElement[numberOfTokens];
// we don't compute t2 in the precomputation since we prefer to
// compute h^beta2 as part of the sigmaBPrime multi-exponentiation
ukat = new UProveKeyAndToken[numberOfTokens];
for (int i = 0; i < numberOfTokens; i++)
{
ukat[i] = new UProveKeyAndToken();
h[i] = gamma.Exponentiate(alpha[i].Multiply(beta0Inverse)); // remove collab issuance blind, if present
t1[i] = Gq.MultiExponentiate(new GroupElement[] { ip.G[0], Gq.G }, new FieldZqElement[] { beta1[i], beta2[i] });
ukat[i].PrivateKey = alpha[i].Invert();
}
state = State.Initialized;
}
/// <summary>
/// Computes the value <c>gamma</c>, an input to the issuance protocol.
/// </summary>
/// <param name="ip">The issuer parameters</param>
/// <param name="A"> The attribute values, or null if the token contains no attributes </param>
/// <param name="TI">The token information field</param>
/// <param name="hd">The device public key, or <c>null</c> if device binding is not supported by the issuer paramters.</param>
/// <returns>The group element gamma </returns>
public static GroupElement ComputeIssuanceInput(IssuerParameters ip, byte[][] A, byte[] TI, GroupElement hd)
{
if (ip == null)
{
throw new ArgumentNullException("Issuer parameters are null");
}
int n = 0;
bool supportDevice = (hd != null);
if (supportDevice && !ip.IsDeviceSupported)
{
throw new InvalidOperationException("Issuer parameters does not support devices");
}
if (A != null)
{
n = A.Length;
}
Group Gq = ip.Gq;
GroupElement[] bases = new GroupElement[n + 1];
FieldZqElement[] exponents = new FieldZqElement[n + 1];
for (int i = 0; i < n; i++)
{
FieldZqElement xi = ComputeXi(ip, i, A[i]);
bases[i] = ip.G[i + 1];
exponents[i] = xi;
}
FieldZqElement xt = ComputeXt(ip, TI, supportDevice);
bases[n] = ip.G[n + 1];
exponents[n] = xt;
GroupElement gamma = ip.G[0] * Gq.MultiExponentiate(bases, exponents);
// Multiply-in the device public key for device-protected tokens
if (supportDevice)
{
gamma = gamma * hd;
}
return(gamma);
}
public void Verify(IssuerParameters ip, int[] disclosed, int[] committed, int pseudonymAttribIndex, GroupElement gs, byte[] message, byte[] messageD, UProveToken upt)
{
try
{
// make sure disclosed list is sorted
if (disclosed == null)
{
// can't be null later, so make it an empty array
disclosed = new int[] { };
}
Array.Sort(disclosed);
Group Gq = ip.Gq;
int n = ip.E.Length;
bool presentPseudonym = false;
if (gs != null && pseudonymAttribIndex != 0)
{
if (pseudonymAttribIndex < 1 || (pseudonymAttribIndex > n && pseudonymAttribIndex != DeviceAttributeIndex))
{
throw new ArgumentException("pseudonymAttribIndex must be between 1 and " + n + " (inclusive)");
}
if (disclosed.Contains(pseudonymAttribIndex))
{
throw new ArgumentException("pseudonymAttribIndex cannot be in the disclosed attribute array");
}
presentPseudonym = true;
}
else // no nym
{
pseudonymAttribIndex = 0;
}
bool verifyCommitments = (committed != null && committed.Length > 0);
if (verifyCommitments)
{
Array.Sort(committed);
}
ProtocolHelper.VerifyTokenSignature(ip, upt);
int dArraySize = disclosed.Length + 2;
GroupElement[] dBases = new GroupElement[dArraySize];
FieldZqElement[] dExponents = new FieldZqElement[dArraySize];
dBases[0] = ip.G[0]; dExponents[0] = ip.Zq.One; // g0^1
dBases[1] = ip.G[n + 1]; dExponents[1] = ProtocolHelper.ComputeXt(ip, upt.TI, upt.IsDeviceProtected); // gt^xt
FieldZqElement[] disclosedX = new FieldZqElement[disclosedAttributes.Length];
int aPreImageArraySize = 2 + (n - disclosed.Length) + (upt.IsDeviceProtected ? 1 : 0);
GroupElement[] aPreImageBases = new GroupElement[aPreImageArraySize];
FieldZqElement[] aPreImageExponents = new FieldZqElement[aPreImageArraySize];
// aPreImage arrays' index 0 values depend on the dArray values; they will be filled out later
aPreImageBases[1] = upt.H; aPreImageExponents[1] = this.r[0]; // h^r0
int dIndex = 0;
int uIndex = 1;
int cIndex = 0;
int pseudonymResponseIndex = 0;
int[] commitmentResponseIndices = verifyCommitments ? new int[committed.Length] : null;
for (int i = 1; i <= n; i++)
{
if (disclosed.Contains(i))
{
disclosedX[dIndex] = ProtocolHelper.ComputeXi(ip, i - 1, disclosedAttributes[dIndex]);
dBases[dIndex + 2] = ip.G[i];
dExponents[dIndex + 2] = disclosedX[dIndex];
dIndex++;
}
else
{
aPreImageBases[uIndex + 1] = ip.G[i]; aPreImageExponents[uIndex + 1] = this.r[uIndex]; // gi^ri
if (presentPseudonym)
{
if (pseudonymAttribIndex == i)
{
pseudonymResponseIndex = uIndex;
}
}
if (verifyCommitments)
{
if (committed.Contains(i))
{
// remember which response correspond to which commitment
commitmentResponseIndices[cIndex] = uIndex;
cIndex++;
}
}
uIndex++;
}
}
if (pseudonymAttribIndex == DeviceAttributeIndex)
{
pseudonymResponseIndex = this.r.Length - 1; // r_d is the last response in the array
}
byte[] unused; // verifier doesn't use the returned message for device
FieldZqElement c = ProtocolHelper.GenerateChallenge(ip, upt, this.a, pseudonymAttribIndex, this.ap, this.ps, message, messageD, disclosed, disclosedX, committed, this.Commitments, out unused);
aPreImageBases[0] = Gq.MultiExponentiate(dBases, dExponents); aPreImageExponents[0] = c.Negate(); // g0.gt^xt.Product[gi^xi]_(for disclosed i)
if (upt.IsDeviceProtected)
{
aPreImageBases[aPreImageArraySize - 1] = ip.Gd; aPreImageExponents[aPreImageArraySize - 1] = this.r[this.r.Length - 1]; // gd^rd
}
HashFunction hash = ip.HashFunction;
hash.Hash(Gq.MultiExponentiate(aPreImageBases, aPreImageExponents));
if (!this.a.SequenceEqual(hash.Digest))
{
throw new InvalidUProveArtifactException("Invalid presentation proof");
}
if (presentPseudonym)
{
hash.Hash(Gq.MultiExponentiate(new GroupElement[] { ps, gs }, new FieldZqElement[] { c, r[pseudonymResponseIndex] }));
if (!this.ap.SequenceEqual(hash.Digest))
{
throw new InvalidUProveArtifactException("Invalid pseudonym");
}
}
if (verifyCommitments)
{
GroupElement[] cBases = new GroupElement[3];
FieldZqElement[] cExponents = new FieldZqElement[3];
cBases[1] = Gq.G;
cBases[2] = ip.G[1];
cExponents[0] = c;
for (int i = 0; i < commitmentResponseIndices.Length; i++)
{
CommitmentValues commitment = this.Commitments[i];
cBases[0] = commitment.TildeC;
cExponents[1] = this.r[commitmentResponseIndices[i]];
cExponents[2] = commitment.TildeR;
hash.Hash(Gq.MultiExponentiate(cBases, cExponents));
if (!commitment.TildeA.SequenceEqual(hash.Digest))
{
throw new InvalidUProveArtifactException("Invalid commitment " + committed[i]);
}
}
}
}
catch (ArgumentException)
{
throw new InvalidUProveArtifactException("Invalid presentation proof");
}
catch (IndexOutOfRangeException)
{
throw new InvalidUProveArtifactException("Invalid presentation proof");
}
}
/// <summary>
/// Generates a presentation proof including optionally presenting a pseudonym, creating attribute commitments, and passing pre-generated random values.
/// </summary>
/// <param name="ip">The issuer parameters corresponding to <code>upkt</code>.</param>
/// <param name="disclosed">An ordered array of disclosed attribute indices.</param>
/// <param name="committed">An ordered array of committed attribute indices.</param>
/// <param name="pseudonymAttribIndex">Index of the attribute used to create a scope-exclusive pseudonym, or 0 if no pseudonym is to be presented. The index must not be part of the disclosed attributes.</param>
/// <param name="gs">The pseudonym scope element, or null if no pseudonym is to be presented.</param>
/// <param name="message">The presentation message.</param>
/// <param name="messageD">The message for the Device, or null.</param>
/// <param name="deviceContext">The active device context, if token is device-protected, or null.</param>
/// <param name="upkt">The U-Proke key and token.</param>
/// <param name="attributes">The token attributes.</param>
/// <param name="preGenW">Optional pregenerated random data for the proof generation.</param>
/// <param name="cpv">Returned commitment private values if commitments are computed.</param>
/// <returns>A presentation proof.</returns>
internal static PresentationProof Generate(IssuerParameters ip, int[] disclosed, int[] committed, int pseudonymAttribIndex, GroupElement gs, byte[] message, byte[] messageD, IDevicePresentationContext deviceContext, UProveKeyAndToken upkt, byte[][] attributes, ProofGenerationRandomData preGenW, out CommitmentPrivateValues cpv)
{
if (upkt.Token.IsDeviceProtected && deviceContext == null)
{
throw new ArgumentNullException("Device context is not initialized");
}
bool generateCommitments = (committed != null && committed.Length > 0);
FieldZqElement[] tildeO = null;
// make sure disclosed and committed lists are sorted
if (disclosed == null)
{
// can't be null later, so make it an empty array
disclosed = new int[] { };
}
Array.Sort(disclosed);
if (generateCommitments)
{
Array.Sort(committed);
}
int n = 0;
if (ip.E != null)
{
n = ip.E.Length;
if (n != attributes.Length)
{
throw new ArgumentException("number of attributes is inconsistent with issuer parameters");
}
}
bool presentPseudonym = false;
if (gs != null)
{
if (pseudonymAttribIndex < 1 || (pseudonymAttribIndex > n && pseudonymAttribIndex != DeviceAttributeIndex))
{
throw new ArgumentException("pseudonymAttribIndex must be between 1 and " + n + " (inclusive)");
}
if (disclosed.Contains(pseudonymAttribIndex))
{
throw new ArgumentException("pseudonymAttribIndex cannot be in the disclosed attribute array");
}
presentPseudonym = true;
}
else if (pseudonymAttribIndex > 0)
{
throw new ArgumentNullException("gs is null");
}
else
{
pseudonymAttribIndex = 0;
}
Group Gq = ip.Gq;
FieldZq Zq = ip.Zq;
FieldZqElement xt = ProtocolHelper.ComputeXt(ip, upkt.Token.TI, upkt.Token.IsDeviceProtected);
ProofGenerationRandomData random;
if (preGenW == null)
{
random = ProofGenerationRandomData.Generate(n - disclosed.Length, generateCommitments ? committed.Length : 0, Zq, upkt.Token.IsDeviceProtected);
}
else
{
random = preGenW;
}
// set up the multi-exponentiation arrays, with h^w0 as the first term
int multiExpArraySize = 1 + (n - disclosed.Length) + (upkt.Token.IsDeviceProtected ? 1 : 0);
GroupElement[] bases = new GroupElement[multiExpArraySize];
FieldZqElement[] exponents = new FieldZqElement[multiExpArraySize];
int multiExpIndex = 0;
bases[multiExpIndex] = upkt.Token.H;
exponents[multiExpIndex++] = random.W0;
FieldZqElement[] x = new FieldZqElement[n];
int uIndex = 0;
int dIndex = 0;
int cIndex = 0;
PresentationProof proof = new PresentationProof();
proof.DisclosedAttributes = new byte[disclosed.Length][];
int pseudonymRandomizerIndex = 0;
if (generateCommitments)
{
proof.Commitments = new CommitmentValues[committed.Length];
tildeO = new FieldZqElement[committed.Length];
}
HashFunction hash = ip.HashFunction;
GroupElement[] cBases = new GroupElement[2] {
Gq.G, ip.G[1]
};
for (int i = 0; i < n; i++)
{
x[i] = ProtocolHelper.ComputeXi(ip, i, attributes[i]);
if (!disclosed.Contains(i + 1))
{
bases[multiExpIndex] = ip.G[i + 1];
exponents[multiExpIndex++] = random.W[uIndex];
if (presentPseudonym)
{
if (pseudonymAttribIndex == (i + 1))
{
pseudonymRandomizerIndex = uIndex;
}
}
if (generateCommitments && committed.Contains(i + 1))
{
GroupElement tildeC = ip.Gq.MultiExponentiate(cBases, new FieldZqElement[2] {
x[i], random.TildeO[cIndex]
});
tildeO[cIndex] = random.TildeO[cIndex];
GroupElement temp2 = ip.Gq.MultiExponentiate(cBases, new FieldZqElement[2] {
random.W[uIndex], random.TildeW[cIndex]
});
hash.Hash(temp2);
byte[] tildeA = hash.Digest;
proof.Commitments[cIndex] = new CommitmentValues(tildeC, tildeA, null);
cIndex++;
}
uIndex++;
}
else if (generateCommitments && committed.Contains(i + 1))
{
throw new ArgumentException("attribute " + (i + 1) + " cannot be both disclosed and committed");
}
else
{
proof.DisclosedAttributes[dIndex] = attributes[i];
dIndex++;
}
}
GroupElement aPreImage;
if (upkt.Token.IsDeviceProtected)
{
GroupElement ad;
// pseudonym computed by device
if (presentPseudonym && pseudonymAttribIndex == DeviceAttributeIndex)
{
GroupElement apPrime;
GroupElement Ps;
ad = deviceContext.GetInitialWitnessesAndPseudonym(gs, out apPrime, out Ps);
hash.Hash(apPrime * gs.Exponentiate(random.Wd));
proof.Ap = hash.Digest;
proof.Ps = Ps;
}
else
{
ad = deviceContext.GetInitialWitness();
}
bases[multiExpIndex] = ip.Gd;
exponents[multiExpIndex++] = random.Wd;
aPreImage = Gq.MultiExponentiate(bases, exponents) * ad;
}
else
{
aPreImage = Gq.MultiExponentiate(bases, exponents);
}
hash.Hash(aPreImage);
proof.a = hash.Digest;
// pseudonym derived from one token attribute
if (presentPseudonym && pseudonymAttribIndex != DeviceAttributeIndex)
{
hash.Hash(gs.Exponentiate(random.W[pseudonymRandomizerIndex]));
proof.Ap = hash.Digest;
proof.Ps = gs.Exponentiate(x[pseudonymAttribIndex - 1]);
}
byte[] mdPrime;
FieldZqElement c = ProtocolHelper.GenerateChallenge(ip, upkt.Token, proof.a, pseudonymAttribIndex, proof.ap, proof.Ps, message, messageD, disclosed, GetDisclosedX(disclosed, x), committed, proof.Commitments, out mdPrime);
proof.r = new FieldZqElement[1 + n - disclosed.Length + (upkt.Token.IsDeviceProtected ? 1 : 0)]; // r_0, {r_i} for undisclosed i, r_d
proof.r[0] = c * upkt.PrivateKey + random.W0;
uIndex = 1;
for (int i = 1; i <= n; i++)
{
if (!disclosed.Contains(i))
{
proof.r[uIndex] = c.Negate() * x[i - 1] + random.W[uIndex - 1];
uIndex++;
}
}
if (upkt.Token.IsDeviceProtected)
{
proof.r[proof.r.Length - 1] = deviceContext.GetDeviceResponse(messageD, mdPrime, ip.HashFunctionOID) + random.Wd;
}
if (generateCommitments)
{
for (int i = 0; i < committed.Length; i++)
{
proof.Commitments[i].TildeR = c.Negate() * random.TildeO[i] + random.TildeW[i];
}
}
random.Clear();
cpv = new CommitmentPrivateValues(tildeO);
return(proof);
}
// Verifies the pre-issuance proof, and returns the element gamma needed for the token issuance.
/// <summary>
/// Verifies a pre-issuance proof and returns the element gamma needed for collaborative issuance.
/// </summary>
/// <param name="ipip">The pre-issuance proof parameters for the Issuer</param>
/// <param name="proof">The proof to be verified</param>
/// <param name="message">An optional message to be verified (must match the one signed by the prover)</param>
/// <returns>The group element <c>gamma^beta0</c>, a blinded version of the element gamma used during token issuance.</returns>
/// <exception cref="InvalidUProveArtifactException">Thrown if the proof is invalid.</exception>
public static GroupElement VerifyProof(IssuerPreIssuanceParameters ipip, PreIssuanceProof proof, byte[] message)
{
// Validate paramters first
ipip.Validate();
// extension by Fablei -> need to know the number of attributes involved in this proof -> ip.G.length
int ipGLength = proof.na + 2;
IssuerParameters ip = ipip.IP;
FieldZq Zq = ip.Zq;
Group Gq = ip.Gq;
List <GroupElement> bases = new List <GroupElement>();
List <FieldZqElement> exponents = new List <FieldZqElement>();
GroupElement[] C = null;
GroupElement[] CPrime = null;
FieldZqElement c = Zq.GetElementFromDigest(proof.c);
if (ipip.HasCarryOverAttributes)
{
// validate presentation proof
int[] disclosed = new int[] {};
VerifierPresentationProtocolParameters vppp = new VerifierPresentationProtocolParameters(ipip.SourceIP, disclosed, message, ipip.Tokens);
vppp.Committed = ipip.Corig;
try
{
proof.presentation.Verify(vppp);
}
catch (InvalidUProveArtifactException e)
{
throw new InvalidUProveArtifactException("Failed to verify pre-Issuance proof, presentation proof " + 0 + " failed to verify (" + e.ToString() + ")");
}
// extract the commitments
C = new GroupElement[ipip.C.Length];
CPrime = new GroupElement[ipip.C.Length];
for (int i = 0; i < C.Length; i++)
{
C[i] = proof.presentation.Commitments[i].TildeC;
// Compute the CPrime[i] values.
bases = new List <GroupElement>();
exponents = new List <FieldZqElement>();
bases.Add(C[i]);
exponents.Add(c);
bases.Add(Gq.G);
exponents.Add(proof.GetResponse("sx" + ipip.C[i]));
bases.Add(ip.G[1]);
exponents.Add(proof.GetResponse("sR" + i));
CPrime[i] = Gq.MultiExponentiate(bases.ToArray(), exponents.ToArray());
//Debug.WriteLine("CPrime[i] = " + BitConverter.ToString(CPrime[i].GetEncoded()));
}
}
// Compute D'
FieldZqElement sd = proof.GetResponse("sD");
GroupElement DPrime = Gq.MultiExponentiate(proof.Ch0, proof.h0, c, c.Negate()); // TODO: add Inverse() to group element to simplify this
DPrime = DPrime.Multiply(Gq.G.Exponentiate(sd));
//Debug.WriteLine("DPrime = " + BitConverter.ToString(DPrime.GetEncoded()));
// Compute T'
FieldZqElement sBeta0 = proof.GetResponse("sBeta0");
GroupElement TPrime = Gq.MultiExponentiate(proof.Ch0, proof.CGamma, c, sBeta0);
//Debug.WriteLine("TPrime = " + BitConverter.ToString(TPrime.GetEncoded()));
// Compute gammaK (product of known attributes)
bases = new List <GroupElement>();
exponents = new List <FieldZqElement>();
//int t = ip.G.Length-1;
// extension by Fablei
int t = ipGLength - 1;
FieldZqElement xt = ProtocolHelper.ComputeXt(ip, ipip.TI, ipip.DeviceProtected);
bases.Add(ip.G[0]);
exponents.Add(ip.Zq.One);
bases.Add(ip.G[t]);
exponents.Add(xt); // gammaK = g0*(gt^xt)
for (int i = 1; i < ipGLength - 1; i++)
{
if (ipip.K.Contains(i))
{
FieldZqElement xi = ProtocolHelper.ComputeXi(ip, i - 1, ipip.Attributes[i - 1]);
bases.Add(ip.G[i]);
exponents.Add(xi);
}
}
GroupElement gammaK = Gq.MultiExponentiate(bases.ToArray(), exponents.ToArray());
// Compute Cgamma'
bases = new List <GroupElement>();
exponents = new List <FieldZqElement>();
bases.Add(proof.CGamma);
exponents.Add(c);
bases.Add(gammaK);
exponents.Add(c.Negate()); // TODO: do with one exp; i.e., (CGamma/gammaK)^c
for (int i = 1; i < ipGLength - 1; i++)
{
if (!ipip.K.Contains(i))
{
FieldZqElement sxi = proof.GetResponse("sx" + i);
bases.Add(ip.G[i]);
exponents.Add(sxi);
}
}
bases.Add(Gq.G);
exponents.Add(proof.GetResponse("sRho"));
GroupElement CgammaPrime = Gq.MultiExponentiate(bases.ToArray(), exponents.ToArray());
// TODO: if deviceprotected multiply device base/response.
//Debug.WriteLine("CgammaPrime = " + BitConverter.ToString(CgammaPrime.GetEncoded()));
// Recompute challenge
byte[] cPrime = ComputeChallenge(ip, proof.h0, proof.CGamma, proof.Ch0, C, DPrime, CgammaPrime, TPrime, CPrime, message);
//Debug.WriteLine("c' = " + BitConverter.ToString(cPrime));
if (!cPrime.SequenceEqual <byte>(proof.c))
{
throw new InvalidUProveArtifactException("invalid proof");
}
return(proof.h0);
}
/// <summary>
/// Create a new pre-issuance proof.
/// </summary>
/// <param name="pipp">The prover parameters.</param>
/// <param name="beta0">The random blinding value used to create the proof, output so that the prover can use it during the issuance protocol</param>
/// <param name="message">An optional message to sign while creating the proof.</param>
/// <returns></returns>
public static PreIssuanceProof CreateProof(ProverPreIssuanceParameters pipp, out FieldZqElement beta0, byte[] message)
{
// validate paramters first
pipp.Validate();
bool supportDevice = (pipp.DevicePublicKey == null) ? false : true;
IssuerParameters ip = pipp.IP;
FieldZq Zq = ip.Zq;
Group Gq = ip.Gq;
Dictionary <string, FieldZqElement> responses = new Dictionary <string, FieldZqElement>();
// these will be used if there is a carry-over attribute
CommitmentPrivateValues cpv = null;
PresentationProof presProof = null;
GroupElement[] C = null;
GroupElement[] tildeC = null;
FieldZqElement[] tildeR = null;
// extension by Fablei -> needs to calculate the ip.G.Length -> pipp.Attributes.Length + 2
int ipGLength = pipp.Attributes.Length + 2;
// Generate random values
beta0 = Zq.GetRandomElement(true);
FieldZqElement tildeBeta0 = Zq.GetRandomElement(true);
FieldZqElement rho = Zq.GetRandomElement(true);
FieldZqElement tildeRho = Zq.GetRandomElement(true);
FieldZqElement tilde_d = Zq.GetRandomElement(true);
FieldZqElement[] tildeX = new FieldZqElement[ipGLength - 1];
for (int i = 1; i < ipGLength - 1; i++)
{
if (!pipp.K.Contains(i))
{
tildeX[i] = Zq.GetRandomElement(true);
}
}
// Compute the U-Prove presentation proof, if there are carry-over attributes
if (pipp.HasCarryOverAttributes)
{
// generate the presentation proof
int[] disclosed = new int[] { };
ProverPresentationProtocolParameters pppp = new ProverPresentationProtocolParameters(pipp.SourceIP, disclosed, message, pipp.KeyAndToken, pipp.SourceAttributes);
pppp.Committed = pipp.Corig;
// TODO: What if the source token is device protected? need to handle this as well. (a pointer to the device should be included in pipp
//if (device != null)
//{
// pppp.SetDeviceData(deviceMessage, device.GetPresentationContext());
//}-
// For now just fail:
if (pipp.KeyAndToken.Token.IsDeviceProtected)
{
throw new NotImplementedException("Device protected tokens may not be used for carry-over attributes");
}
presProof = PresentationProof.Generate(pppp, out cpv);
//set C
C = new GroupElement[pipp.C.Length];
// Generate random values for the commitment randomizers
tildeR = Zq.GetRandomElements(pipp.C.Length, true);
tildeC = new GroupElement[C.Length];
for (int i = 0; i < C.Length; i++)
{
C[i] = presProof.Commitments[i].TildeC;
tildeC[i] = Gq.MultiExponentiate(Gq.G, ip.G[1], tildeX[pipp.C[i]], tildeR[i]);
}
} // end if cary-over attributes
// Compute gamma
GroupElement gamma = ProtocolHelper.ComputeIssuanceInput(ip, pipp.Attributes, pipp.TI, pipp.DevicePublicKey);
// Compute h0, Cgamma, Ch0, tildeD, tildeT:
GroupElement h0 = gamma.Exponentiate(beta0);
GroupElement Cgamma = gamma.Multiply(Gq.G.Exponentiate(rho)); // Cgamma = gamma*(g^rho)
GroupElement Ch0 = Cgamma.Exponentiate(beta0);
GroupElement tildeD = Gq.G.Exponentiate(tilde_d);
GroupElement tildeT = Cgamma.Exponentiate(tildeBeta0);
// Compute tildeCgamma:
List <GroupElement> bases = new List <GroupElement>();
List <FieldZqElement> exponents = new List <FieldZqElement>();
bases.Add(Gq.G);
exponents.Add(tildeRho);
for (int i = 1; i < ipGLength - 1; i++)
{
if (!pipp.K.Contains(i)) // i \not\in K
{
bases.Add(ip.G[i]);
exponents.Add(tildeX[i]);
}
}
GroupElement tildeCgamma = Gq.MultiExponentiate(bases.ToArray(), exponents.ToArray());
// TODO: if device protected, then multiply tildeCgamma by the public key
// Note: We leave TI out, (i.e., (g_t)^(x_t) because t \in K implicitly.
// Compute the challenge
byte[] c = ComputeChallenge(ip, h0, Cgamma, Ch0, C, tildeD, tildeCgamma, tildeT, tildeC, message);
FieldZqElement negc = Zq.GetElementFromDigest(c).Negate();
// Compute the responses
responses.Add("sBeta0", tildeBeta0.Add(beta0.Multiply(negc))); // sBeta0 = tildeBeta0 - beta0*c
responses.Add("sD", tilde_d.Add(beta0.Multiply(rho).Multiply(negc))); // sD = tilde_d - beta0*rho*c
responses.Add("sRho", tildeRho.Add(rho.Multiply(negc))); // sRho = tildeRho - rho*c
for (int i = 1; i < ipGLength - 1; i++)
{
if (!pipp.K.Contains(i)) // in \not\in K
{
FieldZqElement xi = ProtocolHelper.ComputeXi(ip, i - 1, pipp.Attributes[i - 1]);
responses.Add("sx" + i, tildeX[i].Add(xi.Multiply(negc))); // sxi = tildeX[i] - xi*c
}
}
if (pipp.HasCarryOverAttributes)
{
for (int i = 0; i < C.Length; i++)
{
responses.Add("sR" + i, tildeR[i].Add(cpv.TildeO[i].Multiply(negc))); // sRi = tildeR[i] - tildeO[i]*c
}
}
return(new PreIssuanceProof(h0, Cgamma, Ch0, c, responses,
pipp.HasCarryOverAttributes ? presProof : null, pipp.Attributes.Length));
}
