1 files changed, 41 insertions, 0 deletions
diff --git a/src/crypto/sha3.h b/src/crypto/sha3.h
new file mode 100644
index 0000000000..88d8c1204d
--- /dev/null
+++ b/src/crypto/sha3.h
@@ -0,0 +1,41 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_CRYPTO_SHA3_H
+#define BITCOIN_CRYPTO_SHA3_H
+
+#include <span.h>
+
+#include <stdint.h>
+#include <stdlib.h>
+
+//! The Keccak-f[1600] transform.
+void KeccakF(uint64_t (&st)[25]);
+
+class SHA3_256
+{
+private:
+    uint64_t m_state[25] = {0};
+    unsigned char m_buffer[8];
+    unsigned m_bufsize = 0;
+    unsigned m_pos = 0;
+
+    //! Sponge rate in bits.
+    static constexpr unsigned RATE_BITS = 1088;
+
+    //! Sponge rate expressed as a multiple of the buffer size.
+    static constexpr unsigned RATE_BUFFERS = RATE_BITS / (8 * sizeof(m_buffer));
+
+    static_assert(RATE_BITS % (8 * sizeof(m_buffer)) == 0, "Rate must be a multiple of 8 bytes");
+
+public:
+    static constexpr size_t OUTPUT_SIZE = 32;
+
+    SHA3_256() {}
+    SHA3_256& Write(Span<const unsigned char> data);
+    SHA3_256& Finalize(Span<unsigned char> output);
+    SHA3_256& Reset();
+};
+
+#endif // BITCOIN_CRYPTO_SHA3_H