/// <summary>
/// Creates and returns the payload to send to the other participant during round 3.
///
/// See JPakeParticipant for more details on round 3.
///
/// After execution, the State state} will be STATE_ROUND_3_CREATED.
/// Throws InvalidOperationException if called prior to CalculateKeyingMaterial, or multiple
/// times.
/// </summary>
/// <param name="keyingMaterial">The keying material as returned from CalculateKeyingMaterial().</param>
public virtual JPakeRound3Payload CreateRound3PayloadToSend(BigInteger keyingMaterial)
{
if (this.state >= STATE_ROUND_3_CREATED)
{
throw new InvalidOperationException("Round 3 payload already created for " + this.participantId);
}
if (this.state < STATE_KEY_CALCULATED)
{
throw new InvalidOperationException("Keying material must be calculated prior to creating round 3 payload for " + this.participantId);
}
BigInteger macTag = JPakeUtilities.CalculateMacTag(
this.participantId,
this.partnerParticipantId,
this.gx1,
this.gx2,
this.gx3,
this.gx4,
keyingMaterial,
this.digest);
this.state = STATE_ROUND_3_CREATED;
return(new JPakeRound3Payload(participantId, macTag));
}
/// <summary>
/// Validates the payload received from the other participant during round 3.
///
/// See JPakeParticipant for more details on round 3.
///
/// After execution, the State state will be STATE_ROUND_3_VALIDATED.
///
/// Throws CryptoException if validation fails. Throws InvalidOperationException if called prior to
/// CalculateKeyingMaterial or multiple times
/// </summary>
/// <param name="round3PayloadReceived">The round 3 payload received from the other participant.</param>
/// <param name="keyingMaterial">The keying material as returned from CalculateKeyingMaterial().</param>
public virtual void ValidateRound3PayloadReceived(JPakeRound3Payload round3PayloadReceived, BigInteger keyingMaterial)
{
if (this.state >= STATE_ROUND_3_VALIDATED)
{
throw new InvalidOperationException("Validation already attempted for round 3 payload for " + this.participantId);
}
if (this.state < STATE_KEY_CALCULATED)
{
throw new InvalidOperationException("Keying material must be calculated prior to validating round 3 payload for " + this.participantId);
}
JPakeUtilities.ValidateParticipantIdsDiffer(participantId, round3PayloadReceived.ParticipantId);
JPakeUtilities.ValidateParticipantIdsEqual(this.partnerParticipantId, round3PayloadReceived.ParticipantId);
JPakeUtilities.ValidateMacTag(
this.participantId,
this.partnerParticipantId,
this.gx1,
this.gx2,
this.gx3,
this.gx4,
keyingMaterial,
this.digest,
round3PayloadReceived.MacTag);
// Clear the rest of the fields.
this.gx1 = null;
this.gx2 = null;
this.gx3 = null;
this.gx4 = null;
this.state = STATE_ROUND_3_VALIDATED;
}
public JPakeRound2Payload(string participantId, BigInteger a, BigInteger[] knowledgeProofForX2s)
{
JPakeUtilities.ValidateNotNull(participantId, "participantId");
JPakeUtilities.ValidateNotNull(a, "a");
JPakeUtilities.ValidateNotNull(knowledgeProofForX2s, "knowledgeProofForX2s");
this.participantId = participantId;
this.a = a;
this.knowledgeProofForX2s = new BigInteger[knowledgeProofForX2s.Length];
knowledgeProofForX2s.CopyTo(this.knowledgeProofForX2s, 0);
}
public JPakeRound1Payload(string participantId, BigInteger gx1, BigInteger gx2, BigInteger[] knowledgeProofForX1, BigInteger[] knowledgeProofForX2)
{
JPakeUtilities.ValidateNotNull(participantId, "participantId");
JPakeUtilities.ValidateNotNull(gx1, "gx1");
JPakeUtilities.ValidateNotNull(gx2, "gx2");
JPakeUtilities.ValidateNotNull(knowledgeProofForX1, "knowledgeProofForX1");
JPakeUtilities.ValidateNotNull(knowledgeProofForX2, "knowledgeProofForX2");
this.participantId = participantId;
this.gx1 = gx1;
this.gx2 = gx2;
this.knowledgeProofForX1 = new BigInteger[knowledgeProofForX1.Length];
Array.Copy(knowledgeProofForX1, this.knowledgeProofForX1, knowledgeProofForX1.Length);
this.knowledgeProofForX2 = new BigInteger[knowledgeProofForX2.Length];
Array.Copy(knowledgeProofForX2, this.knowledgeProofForX2, knowledgeProofForX2.Length);
}
/// <summary>
/// Creates and returns the payload to send to the other participant during round 1.
///
/// After execution, the State state} will be STATE_ROUND_1_CREATED}.
/// </summary>
public virtual JPakeRound1Payload CreateRound1PayloadToSend()
{
if (this.state >= STATE_ROUND_1_CREATED)
{
throw new InvalidOperationException("Round 1 payload already created for " + this.participantId);
}
this.x1 = JPakeUtilities.GenerateX1(q, random);
this.x2 = JPakeUtilities.GenerateX2(q, random);
this.gx1 = JPakeUtilities.CalculateGx(p, g, x1);
this.gx2 = JPakeUtilities.CalculateGx(p, g, x2);
BigInteger[] knowledgeProofForX1 = JPakeUtilities.CalculateZeroKnowledgeProof(p, q, g, gx1, x1, participantId, digest, random);
BigInteger[] knowledgeProofForX2 = JPakeUtilities.CalculateZeroKnowledgeProof(p, q, g, gx2, x2, participantId, digest, random);
this.state = STATE_ROUND_1_CREATED;
return(new JPakeRound1Payload(participantId, gx1, gx2, knowledgeProofForX1, knowledgeProofForX2));
}
/// <summary>
/// Validates the payload received from the other participant during round 1.
///
/// Must be called prior to CreateRound2PayloadToSend().
///
/// After execution, the State state will be STATE_ROUND_1_VALIDATED.
///
/// Throws CryptoException if validation fails. Throws InvalidOperationException
/// if called multiple times.
/// </summary>
public virtual void ValidateRound1PayloadReceived(JPakeRound1Payload round1PayloadReceived)
{
if (this.state >= STATE_ROUND_1_VALIDATED)
{
throw new InvalidOperationException("Validation already attempted for round 1 payload for " + this.participantId);
}
this.partnerParticipantId = round1PayloadReceived.ParticipantId;
this.gx3 = round1PayloadReceived.Gx1;
this.gx4 = round1PayloadReceived.Gx2;
BigInteger[] knowledgeProofForX3 = round1PayloadReceived.KnowledgeProofForX1;
BigInteger[] knowledgeProofForX4 = round1PayloadReceived.KnowledgeProofForX2;
JPakeUtilities.ValidateParticipantIdsDiffer(participantId, round1PayloadReceived.ParticipantId);
JPakeUtilities.ValidateGx4(gx4);
JPakeUtilities.ValidateZeroKnowledgeProof(p, q, g, gx3, knowledgeProofForX3, round1PayloadReceived.ParticipantId, digest);
JPakeUtilities.ValidateZeroKnowledgeProof(p, q, g, gx4, knowledgeProofForX4, round1PayloadReceived.ParticipantId, digest);
this.state = STATE_ROUND_1_VALIDATED;
}
/// <summary>
/// Creates and returns the payload to send to the other participant during round 2.
///
/// ValidateRound1PayloadReceived(JPakeRound1Payload) must be called prior to this method.
///
/// After execution, the State state will be STATE_ROUND_2_CREATED.
///
/// Throws InvalidOperationException if called prior to ValidateRound1PayloadReceived(JPakeRound1Payload), or multiple times
/// </summary>
public virtual JPakeRound2Payload CreateRound2PayloadToSend()
{
if (this.state >= STATE_ROUND_2_CREATED)
{
throw new InvalidOperationException("Round 2 payload already created for " + this.participantId);
}
if (this.state < STATE_ROUND_1_VALIDATED)
{
throw new InvalidOperationException("Round 1 payload must be validated prior to creating round 2 payload for " + this.participantId);
}
BigInteger gA = JPakeUtilities.CalculateGA(p, gx1, gx3, gx4);
BigInteger s = JPakeUtilities.CalculateS(password);
BigInteger x2s = JPakeUtilities.CalculateX2s(q, x2, s);
BigInteger A = JPakeUtilities.CalculateA(p, q, gA, x2s);
BigInteger[] knowledgeProofForX2s = JPakeUtilities.CalculateZeroKnowledgeProof(p, q, gA, A, x2s, participantId, digest, random);
this.state = STATE_ROUND_2_CREATED;
return(new JPakeRound2Payload(participantId, A, knowledgeProofForX2s));
}
/// <summary>
/// Validates the payload received from the other participant during round 2.
/// Note that this DOES NOT detect a non-common password.
/// The only indication of a non-common password is through derivation
/// of different keys (which can be detected explicitly by executing round 3 and round 4)
///
/// Must be called prior to CalculateKeyingMaterial().
///
/// After execution, the State state will be STATE_ROUND_2_VALIDATED.
///
/// Throws CryptoException if validation fails. Throws
/// InvalidOperationException if called prior to ValidateRound1PayloadReceived(JPakeRound1Payload), or multiple times
/// </summary>
public virtual void ValidateRound2PayloadReceived(JPakeRound2Payload round2PayloadReceived)
{
if (this.state >= STATE_ROUND_2_VALIDATED)
{
throw new InvalidOperationException("Validation already attempted for round 2 payload for " + this.participantId);
}
if (this.state < STATE_ROUND_1_VALIDATED)
{
throw new InvalidOperationException("Round 1 payload must be validated prior to validation round 2 payload for " + this.participantId);
}
BigInteger gB = JPakeUtilities.CalculateGA(p, gx3, gx1, gx2);
this.b = round2PayloadReceived.A;
BigInteger[] knowledgeProofForX4s = round2PayloadReceived.KnowledgeProofForX2s;
JPakeUtilities.ValidateParticipantIdsDiffer(participantId, round2PayloadReceived.ParticipantId);
JPakeUtilities.ValidateParticipantIdsEqual(this.partnerParticipantId, round2PayloadReceived.ParticipantId);
JPakeUtilities.ValidateGa(gB);
JPakeUtilities.ValidateZeroKnowledgeProof(p, q, gB, b, knowledgeProofForX4s, round2PayloadReceived.ParticipantId, digest);
this.state = STATE_ROUND_2_VALIDATED;
}
/// <summary>
/// Constructor for a new JPakeParticipant.
///
/// After construction, the State state will be STATE_INITIALIZED.
///
/// Throws NullReferenceException if any argument is null. Throws
/// ArgumentException if password is empty.
/// </summary>
/// <param name="participantId">Unique identifier of this participant.
/// The two participants in the exchange must NOT share the same id.</param>
/// <param name="password">Shared secret.
/// A defensive copy of this array is made (and cleared once CalculateKeyingMaterial() is called).
/// Caller should clear the input password as soon as possible.</param>
/// <param name="group">Prime order group. See JPakePrimeOrderGroups for standard groups.</param>
/// <param name="digest">Digest to use during zero knowledge proofs and key confirmation
/// (SHA-256 or stronger preferred).</param>
/// <param name="random">Source of secure random data for x1 and x2, and for the zero knowledge proofs.</param>
public JPakeParticipant(string participantId, char[] password, JPakePrimeOrderGroup group, IDigest digest, SecureRandom random)
{
JPakeUtilities.ValidateNotNull(participantId, "participantId");
JPakeUtilities.ValidateNotNull(password, "password");
JPakeUtilities.ValidateNotNull(group, "p");
JPakeUtilities.ValidateNotNull(digest, "digest");
JPakeUtilities.ValidateNotNull(random, "random");
if (password.Length == 0)
{
throw new ArgumentException("Password must not be empty.");
}
this.participantId = participantId;
// Create a defensive copy so as to fully encapsulate the password.
//
// This array will contain the password for the lifetime of this
// participant BEFORE CalculateKeyingMaterial() is called.
//
// i.e. When CalculateKeyingMaterial() is called, the array will be cleared
// in order to remove the password from memory.
//
// The caller is responsible for clearing the original password array
// given as input to this constructor.
this.password = new char[password.Length];
Array.Copy(password, this.password, password.Length);
this.p = group.P;
this.q = group.Q;
this.g = group.G;
this.digest = digest;
this.random = random;
this.state = STATE_INITIALIZED;
}
/// <summary>
/// Constructor used by the pre-approved groups in JPakePrimeOrderGroups.
/// These pre-approved groups can avoid the expensive checks.
/// User-specified groups should not use this constructor.
/// </summary>
public JPakePrimeOrderGroup(BigInteger p, BigInteger q, BigInteger g, bool skipChecks)
{
JPakeUtilities.ValidateNotNull(p, "p");
JPakeUtilities.ValidateNotNull(q, "q");
JPakeUtilities.ValidateNotNull(g, "g");
if (!skipChecks)
{
if (!p.Subtract(JPakeUtilities.One).Mod(q).Equals(JPakeUtilities.Zero))
{
throw new ArgumentException("p-1 must be evenly divisible by q");
}
if (g.CompareTo(BigInteger.Two) == -1 || g.CompareTo(p.Subtract(JPakeUtilities.One)) == 1)
{
throw new ArgumentException("g must be in [2, p-1]");
}
if (!g.ModPow(q, p).Equals(JPakeUtilities.One))
{
throw new ArgumentException("g^q mod p must equal 1");
}
// Note these checks do not guarantee that p and q are prime.
// We just have reasonable certainty that they are prime.
if (!p.IsProbablePrime(20))
{
throw new ArgumentException("p must be prime");
}
if (!q.IsProbablePrime(20))
{
throw new ArgumentException("q must be prime");
}
}
this.p = p;
this.q = q;
this.g = g;
}
/// <summary>
/// Calculates and returns the key material.
/// A session key must be derived from this key material using a secure key derivation function (KDF).
/// The KDF used to derive the key is handled externally (i.e. not by JPakeParticipant).
///
/// The keying material will be identical for each participant if and only if
/// each participant's password is the same. i.e. If the participants do not
/// share the same password, then each participant will derive a different key.
/// Therefore, if you immediately start using a key derived from
/// the keying material, then you must handle detection of incorrect keys.
/// If you want to handle this detection explicitly, you can optionally perform
/// rounds 3 and 4. See JPakeParticipant for details on how to execute
/// rounds 3 and 4.
///
/// The keying material will be in the range <tt>[0, p-1]</tt>.
///
/// ValidateRound2PayloadReceived(JPakeRound2Payload) must be called prior to this method.
///
/// As a side effect, the internal password array is cleared, since it is no longer needed.
///
/// After execution, the State state will be STATE_KEY_CALCULATED.
///
/// Throws InvalidOperationException if called prior to ValidateRound2PayloadReceived(JPakeRound2Payload),
/// or if called multiple times.
/// </summary>
public virtual BigInteger CalculateKeyingMaterial()
{
if (this.state >= STATE_KEY_CALCULATED)
{
throw new InvalidOperationException("Key already calculated for " + participantId);
}
if (this.state < STATE_ROUND_2_VALIDATED)
{
throw new InvalidOperationException("Round 2 payload must be validated prior to creating key for " + participantId);
}
BigInteger s = JPakeUtilities.CalculateS(password);
// Clear the password array from memory, since we don't need it anymore.
// Also set the field to null as a flag to indicate that the key has already been calculated.
Array.Clear(password, 0, password.Length);
this.password = null;
BigInteger keyingMaterial = JPakeUtilities.CalculateKeyingMaterial(p, q, gx4, x2, s, b);
// Clear the ephemeral private key fields as well.
// Note that we're relying on the garbage collector to do its job to clean these up.
// The old objects will hang around in memory until the garbage collector destroys them.
//
// If the ephemeral private keys x1 and x2 are leaked,
// the attacker might be able to brute-force the password.
this.x1 = null;
this.x2 = null;
this.b = null;
// Do not clear gx* yet, since those are needed by round 3.
this.state = STATE_KEY_CALCULATED;
return(keyingMaterial);
}