Implement validator and basic solver for Equihash

src/crypto/equihash.h

@@ -0,0 +1,75 @@
+// Copyright (c) 2016 Jack Grigg
+// Copyright (c) 2016 The Zcash developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_EQUIHASH_H
+#define BITCOIN_EQUIHASH_H
+
+#include "crypto/sha256.h"
+#include "utilstrencodings.h"
+
+#include "sodium.h"
+
+#include <cstring>
+#include <set>
+#include <vector>
+
+typedef crypto_generichash_blake2b_state eh_HashState;
+typedef uint32_t eh_index;
+
+struct invalid_params { };
+
+class StepRow
+{
+private:
+    unsigned char* hash;
+    unsigned int len;
+    std::vector<eh_index> indices;
+
+public:
+    StepRow(unsigned int n, const eh_HashState& base_state, eh_index i);
+    ~StepRow();
+
+    StepRow(const StepRow& a);
+    StepRow& operator=(const StepRow& a);
+    StepRow& operator^=(const StepRow& a);
+
+    void TrimHash(int l);
+    bool IsZero();
+    bool IndicesBefore(const StepRow& a) { return indices[0] < a.indices[0]; }
+    std::vector<eh_index> GetSolution() { return std::vector<eh_index>(indices); }
+    std::string GetHex() { return HexStr(hash, hash+len); }
+
+    friend inline const StepRow operator^(const StepRow& a, const StepRow& b) {
+        if (a.indices[0] < b.indices[0]) { return StepRow(a) ^= b; }
+        else { return StepRow(b) ^= a; }
+    }
+    friend inline bool operator==(const StepRow& a, const StepRow& b) { return memcmp(a.hash, b.hash, a.len) == 0; }
+    friend inline bool operator<(const StepRow& a, const StepRow& b) { return memcmp(a.hash, b.hash, a.len) < 0; }
+
+    friend bool HasCollision(StepRow& a, StepRow& b, int l);
+    friend bool DistinctIndices(const StepRow& a, const StepRow& b);
+};
+
+bool HasCollision(StepRow& a, StepRow& b, int l);
+bool DistinctIndices(const StepRow& a, const StepRow& b);
+
+class Equihash
+{
+private:
+    unsigned int n;
+    unsigned int k;
+
+public:
+    Equihash(unsigned int n, unsigned int k);
+
+    inline unsigned int CollisionBitLength() { return n/(k+1); }
+    inline unsigned int CollisionByteLength() { return CollisionBitLength()/8; }
+
+    int InitialiseState(eh_HashState& base_state);
+    std::set<std::vector<eh_index>> BasicSolve(const eh_HashState& base_state);
+    bool IsValidSolution(const eh_HashState& base_state, std::vector<eh_index> soln);
+};
+
+#endif // BITCOIN_EQUIHASH_H