Refactor ZKP class to use ProofProvider for HMAC and salt generation;…

… remove old ZKP implementation

CHANGELOG.md

@@ -0,0 +1,36 @@
+# Changelog
+
+## [Unreleased]
+
+### Added
+- New method for range proofs (`ProveRange` and `VerifyRange`).
+- Support for time-based proofs (`ProveTimestamp` and `VerifyTimestamp`).
+- Support for proving set membership (`ProveSetMembership` and `VerifySetMembership`).
+
+### Changed
+- Updated HMAC implementation to use more secure random salts.
+
+### Fixed
+- Bug in age verification logic that caused incorrect validation for dates close to the required age.
+
+---
+
+## [1.1.0] - 2025-01-01
+
+### Added
+- Proof of Balance feature (`ProveBalance` and `VerifyBalance`).
+- Salt generation improvements for stronger proofs.
+
+### Changed
+- Refactored `ZKP` class to improve performance and modularity.
+
+### Fixed
+- Fixed an issue where incorrect salt generation would sometimes lead to hash mismatches.
+
+---
+
+## [1.0.0] - 2025-01-01
+
+### Initial release
+- Proof of Age feature (`ProveAge` and `VerifyAge`).
+- Proof of Balance feature (`ProveBalance` and `VerifyBalance`).

ZkpSharp.Tests/ZKPTests.cs

@@ -1,5 +1,7 @@
 using System;
 using Xunit;
+using ZkpSharp.Core;
+using ZkpSharp.Security;
 
 namespace ZkpSharp.Tests
 {
@@ -8,7 +10,8 @@ public class ZKPTests
         [Fact]
         public void TestProveAndVerifyAge_ValidAge_ShouldPass()
         {
-            var zkp = new ZKP();
+            var proofProvider = new ProofProvider();
+            var zkp = new ZKP(proofProvider);
             var dateOfBirth = new DateTime(2000, 1, 1);  // Age 25
             var (proof, salt) = zkp.ProveAge(dateOfBirth);
 
@@ -18,7 +21,8 @@ public void TestProveAndVerifyAge_ValidAge_ShouldPass()
         [Fact]
         public void TestProveAndVerifyAge_InsufficientAge_ShouldFail()
         {
-            var zkp = new ZKP();
+            var proofProvider = new ProofProvider();
+            var zkp = new ZKP(proofProvider);
             var dateOfBirth = new DateTime(2010, 1, 1);  // Age 15
 
             var exception = Assert.Throws<ArgumentException>(() => zkp.ProveAge(dateOfBirth));
@@ -28,7 +32,8 @@ public void TestProveAndVerifyAge_InsufficientAge_ShouldFail()
         [Fact]
         public void TestProveAndVerifyBalance_ValidBalance_ShouldPass()
         {
-            var zkp = new ZKP();
+            var proofProvider = new ProofProvider();
+            var zkp = new ZKP(proofProvider);
             double userBalance = 1000.0;
             double requestedAmount = 500.0;
 
@@ -41,7 +46,8 @@ public void TestProveAndVerifyBalance_ValidBalance_ShouldPass()
         [Fact]
         public void TestProveAndVerifyBalance_InsufficientBalance_ShouldFail()
         {
-            var zkp = new ZKP();
+            var proofProvider = new ProofProvider();
+            var zkp = new ZKP(proofProvider);
             double userBalance = 300.0;
             double requestedAmount = 500.0;
 
@@ -53,7 +59,8 @@ public void TestProveAndVerifyBalance_InsufficientBalance_ShouldFail()
         [Fact]
         public void TestBalanceVerificationWithSalt_ValidBalance_ShouldPass()
         {
-            var zkp = new ZKP();
+            var proofProvider = new ProofProvider();
+            var zkp = new ZKP(proofProvider);
             double userBalance = 1000.0;
             double requestedAmount = 500.0;
             var (proof, salt) = zkp.ProveBalance(userBalance, requestedAmount);
@@ -64,7 +71,8 @@ public void TestBalanceVerificationWithSalt_ValidBalance_ShouldPass()
         [Fact]
         public void TestBalanceVerificationWithSalt_InsufficientBalance_ShouldFail()
         {
-            var zkp = new ZKP();
+            var proofProvider = new ProofProvider();
+            var zkp = new ZKP(proofProvider);
             double userBalance = 100.0;
             double requestedAmount = 150.0;
 
@@ -75,7 +83,8 @@ public void TestBalanceVerificationWithSalt_InsufficientBalance_ShouldFail()
         [Fact]
         public void TestProveAndVerifyAge_InvalidSalt_ShouldFail()
         {
-            var zkp = new ZKP();
+            var proofProvider = new ProofProvider();
+            var zkp = new ZKP(proofProvider);
             var dateOfBirth = new DateTime(2000, 1, 1);  // Возраст 25 лет
             var (proof, salt) = zkp.ProveAge(dateOfBirth);
 
@@ -87,7 +96,8 @@ public void TestProveAndVerifyAge_InvalidSalt_ShouldFail()
         [Fact]
         public void TestBalanceVerificationWithSalt_InvalidSalt_ShouldFail()
         {
-            var zkp = new ZKP();
+            var proofProvider = new ProofProvider();
+            var zkp = new ZKP(proofProvider);
             double userBalance = 1000.0;
             double requestedAmount = 500.0;
             var (proof, salt) = zkp.ProveBalance(userBalance, requestedAmount);

ZkpSharp/Core/ZKP.cs

@@ -0,0 +1,62 @@
+using ZkpSharp.Security;
+
+namespace ZkpSharp.Core
+{
+    public class ZKP
+    {
+        private const int RequiredAge = 18; 
+        private readonly IProofProvider _proofProvider;
+
+        public ZKP(IProofProvider proofProvider)
+        {
+            _proofProvider = proofProvider;
+        }
+
+        // Proof of Age
+        public (string Proof, string Salt) ProveAge(DateTime dateOfBirth)
+        {
+            if (CalculateAge(dateOfBirth) < RequiredAge)
+            {
+                throw new ArgumentException("Insufficient age");
+            }
+
+            string salt = _proofProvider.GenerateSalt();
+            string proof = _proofProvider.GenerateHMAC(dateOfBirth.ToString("yyyy-MM-dd") + salt);
+            return (proof, salt);
+        }
+
+        public bool VerifyAge(string proof, DateTime dateOfBirth, string salt)
+        {
+            int age = CalculateAge(dateOfBirth);
+            string calculatedProof = _proofProvider.GenerateHMAC(dateOfBirth.ToString("yyyy-MM-dd") + salt);
+            return age >= RequiredAge && _proofProvider.SecureEqual(calculatedProof, proof);
+        }
+
+        private int CalculateAge(DateTime dateOfBirth)
+        {
+            DateTime today = DateTime.UtcNow;
+            int age = today.Year - dateOfBirth.Year;
+            if (dateOfBirth > today.AddYears(-age)) age--; 
+            return age;
+        }
+
+        // Proof of Balance
+        public (string Proof, string Salt) ProveBalance(double balance, double requestedAmount)
+        {
+            if (balance < requestedAmount)
+            {
+                throw new ArgumentException("Insufficient balance");
+            }
+
+            string salt = _proofProvider.GenerateSalt();
+            string proof = _proofProvider.GenerateHMAC(balance.ToString() + salt);
+            return (proof, salt);
+        }
+
+        public bool VerifyBalance(string proof, double requestedAmount, string salt, double balance)
+        {
+            string calculatedProof = _proofProvider.GenerateHMAC(balance.ToString() + salt);
+            return _proofProvider.SecureEqual(calculatedProof, proof) && balance >= requestedAmount;
+        }
+    }
+}

ZkpSharp/Security/ProofProvider.cs

@@ -0,0 +1,60 @@
+using System.Security.Cryptography;
+using System.Text;
+
+namespace ZkpSharp.Security
+{
+    public interface IProofProvider
+    {
+        string GenerateSalt();
+        string GenerateHMAC(string input);
+        bool SecureEqual(string a, string b);
+    }
+
+    public class ProofProvider : IProofProvider
+    {
+        private readonly byte[] _hmacKey;
+
+        public ProofProvider()
+        {
+            _hmacKey = LoadHmacKey();
+        }
+
+        public string GenerateSalt()
+        {
+            byte[] saltBytes = new byte[16];
+            using (var rng = RandomNumberGenerator.Create())
+            {
+                rng.GetBytes(saltBytes);
+            }
+            return Convert.ToBase64String(saltBytes);
+        }
+
+        public string GenerateHMAC(string input)
+        {
+            using (var hmac = new HMACSHA256(_hmacKey))
+            {
+                byte[] hashBytes = hmac.ComputeHash(Encoding.UTF8.GetBytes(input));
+                return Convert.ToBase64String(hashBytes);
+            }
+        }
+
+        public bool SecureEqual(string a, string b)
+        {
+            if (a.Length != b.Length) return false;
+
+            int diff = 0;
+            for (int i = 0; i < a.Length; i++)
+            {
+                diff |= a[i] ^ b[i];
+            }
+
+            return diff == 0;
+        }
+
+        private byte[] LoadHmacKey()
+        {
+            // Load HMAC key from secure storage
+            return new byte[32]; // Here we just return a dummy key
+        }
+    }
+}