Add support for SHA-256 midstate access

ElementsProject · Feb 12, 2019 · 7f65e76 · roconnor-blockstream · Feb 14, 2020 · 7f65e76
1 parent 7a01d4f
commit 7f65e76
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Showing 2 changed files with 31 additions and 0 deletions.
diff --git a/src/crypto/sha256.cpp b/src/crypto/sha256.cpp
@@ -670,6 +670,23 @@ CSHA256& CSHA256::Write(const unsigned char* data, size_t len)
     }
     return *this;
 }
+//
+//void CSHA256::Finalize(unsigned char hash[OUTPUT_SIZE])
+//{
+//    static const unsigned char pad[64] = {0x80};
+//    unsigned char sizedesc[8];
+//    WriteBE64(sizedesc, bytes << 3);
+//    Write(pad, 1 + ((119 - (bytes % 64)) % 64));
+//    Write(sizedesc, 8);
+//    WriteBE32(hash, s[0]);
+//    WriteBE32(hash + 4, s[1]);
+//    WriteBE32(hash + 8, s[2]);
+//    WriteBE32(hash + 12, s[3]);
+//    WriteBE32(hash + 16, s[4]);
+//    WriteBE32(hash + 20, s[5]);
+//    WriteBE32(hash + 24, s[6]);
+//    WriteBE32(hash + 28, s[7]);
+//}
 
 void CSHA256::Finalize(unsigned char hash[OUTPUT_SIZE])
 {
@@ -678,6 +695,11 @@ void CSHA256::Finalize(unsigned char hash[OUTPUT_SIZE])
     WriteBE64(sizedesc, bytes << 3);
     Write(pad, 1 + ((119 - (bytes % 64)) % 64));
     Write(sizedesc, 8);
+    Midstate(hash, NULL, NULL);
+}
+
+void CSHA256::Midstate(unsigned char hash[OUTPUT_SIZE], uint64_t* len, unsigned char *buffer)
+{
     WriteBE32(hash, s[0]);
     WriteBE32(hash + 4, s[1]);
     WriteBE32(hash + 8, s[2]);
@@ -686,6 +708,12 @@ void CSHA256::Finalize(unsigned char hash[OUTPUT_SIZE])
     WriteBE32(hash + 20, s[5]);
     WriteBE32(hash + 24, s[6]);
     WriteBE32(hash + 28, s[7]);
+    if (len) {
+        *len = bytes << 3;
+    }
+    if (buffer) {
+        memcpy(buffer, buf, bytes % 64);
+    }
 }
 
 CSHA256& CSHA256::Reset()

diff --git a/src/crypto/sha256.h b/src/crypto/sha256.h
@@ -23,6 +23,9 @@ class CSHA256
     CSHA256();
     CSHA256& Write(const unsigned char* data, size_t len);
     void Finalize(unsigned char hash[OUTPUT_SIZE]);
+    //TODO: Midstate is a hack'ish speedup that probably should make way for something
+    //akin to the SHA256D64 speedups
+    void Midstate(unsigned char hash[OUTPUT_SIZE], uint64_t* len, unsigned char *buffer);
     CSHA256& Reset();
 };