From 9eb590894f15ff40806039bfd32972fbc260e30d Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter@wuille.net>
Date: Fri, 11 Sep 2020 14:32:50 -0700
Subject: Add TaggedHash function (BIP 340)

This adds the TaggedHash function as defined by BIP340 to the hash module, which
is used in BIP340 and BIP341 to produce domain-separated hashes.
---
 src/hash.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'src/hash.cpp')

diff --git a/src/hash.cpp b/src/hash.cpp
index 83b90ae063..3657b38639 100644
--- a/src/hash.cpp
+++ b/src/hash.cpp
@@ -6,6 +6,7 @@
 #include <crypto/common.h>
 #include <crypto/hmac_sha512.h>
 
+#include <string>
 
 inline uint32_t ROTL32(uint32_t x, int8_t r)
 {
@@ -84,3 +85,12 @@ uint256 SHA256Uint256(const uint256& input)
     CSHA256().Write(input.begin(), 32).Finalize(result.begin());
     return result;
 }
+
+CHashWriter TaggedHash(const std::string& tag)
+{
+    CHashWriter writer(SER_GETHASH, 0);
+    uint256 taghash;
+    CSHA256().Write((const unsigned char*)tag.data(), tag.size()).Finalize(taghash.begin());
+    writer << taghash << taghash;
+    return writer;
+}
-- 
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