diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index c4db2ff7b..2acc72a94 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -38,6 +38,8 @@ add_library(common
   rectangle.h
   scoped_guard.h
   settings_interface.h
+  sha1_digest.cpp
+  sha1_digest.h
   string.cpp
   string.h
   string_util.cpp
diff --git a/src/common/common.vcxproj b/src/common/common.vcxproj
index 15ffc407a..96952793b 100644
--- a/src/common/common.vcxproj
+++ b/src/common/common.vcxproj
@@ -70,6 +70,7 @@
     <ClInclude Include="rectangle.h" />
     <ClInclude Include="scoped_guard.h" />
     <ClInclude Include="settings_interface.h" />
+    <ClInclude Include="sha1_digest.h" />
     <ClInclude Include="string.h" />
     <ClInclude Include="heterogeneous_containers.h" />
     <ClInclude Include="string_util.h" />
@@ -172,6 +173,7 @@
     <ClCompile Include="md5_digest.cpp" />
     <ClCompile Include="minizip_helpers.cpp" />
     <ClCompile Include="progress_callback.cpp" />
+    <ClCompile Include="sha1_digest.cpp" />
     <ClCompile Include="string.cpp" />
     <ClCompile Include="string_util.cpp" />
     <ClCompile Include="thirdparty\StackWalker.cpp">
diff --git a/src/common/common.vcxproj.filters b/src/common/common.vcxproj.filters
index 5cd5a20e5..c931d9b7a 100644
--- a/src/common/common.vcxproj.filters
+++ b/src/common/common.vcxproj.filters
@@ -138,6 +138,7 @@
     <ClInclude Include="threading.h" />
     <ClInclude Include="scoped_guard.h" />
     <ClInclude Include="build_timestamp.h" />
+    <ClInclude Include="sha1_digest.h" />
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="gl\program.cpp">
@@ -251,6 +252,7 @@
     <ClCompile Include="layered_settings_interface.cpp" />
     <ClCompile Include="memory_settings_interface.cpp" />
     <ClCompile Include="threading.cpp" />
+    <ClCompile Include="sha1_digest.cpp" />
   </ItemGroup>
   <ItemGroup>
     <Natvis Include="bitfield.natvis" />
diff --git a/src/common/sha1_digest.cpp b/src/common/sha1_digest.cpp
new file mode 100644
index 000000000..17dd63a44
--- /dev/null
+++ b/src/common/sha1_digest.cpp
@@ -0,0 +1,161 @@
+#include "sha1_digest.h"
+#include <cstring>
+
+// mostly based on this implementation (public domain): https://gist.github.com/jrabbit/1042021
+#define rol(value, bits) (((value) << (bits)) | ((value) >> (32 - (bits))))
+
+/* blk0() and blk() perform the initial expand. */
+/* I got the idea of expanding during the round function from SSLeay */
+#define blk0(i) (block->l[i] = (rol(block->l[i],24)&0xFF00FF00) \
+    |(rol(block->l[i],8)&0x00FF00FF))
+#define blk(i) (block->l[i&15] = rol(block->l[(i+13)&15]^block->l[(i+8)&15] \
+    ^block->l[(i+2)&15]^block->l[i&15],1))
+
+/* (R0+R1), R2, R3, R4 are the different operations used in SHA1 */
+#define R0(v,w,x,y,z,i) z+=((w&(x^y))^y)+blk0(i)+0x5A827999+rol(v,5);w=rol(w,30);
+#define R1(v,w,x,y,z,i) z+=((w&(x^y))^y)+blk(i)+0x5A827999+rol(v,5);w=rol(w,30);
+#define R2(v,w,x,y,z,i) z+=(w^x^y)+blk(i)+0x6ED9EBA1+rol(v,5);w=rol(w,30);
+#define R3(v,w,x,y,z,i) z+=(((w|x)&y)|(w&x))+blk(i)+0x8F1BBCDC+rol(v,5);w=rol(w,30);
+#define R4(v,w,x,y,z,i) z+=(w^x^y)+blk(i)+0xCA62C1D6+rol(v,5);w=rol(w,30);
+
+
+/* Hash a single 512-bit block. This is the core of the algorithm. */
+
+static void SHA1Transform(u32 state[5], const unsigned char buffer[64])
+{
+  u32 a, b, c, d, e;
+  typedef union {
+    unsigned char c[64];
+    u32 l[16];
+  } CHAR64LONG16;
+
+  CHAR64LONG16 block[1];  /* use array to appear as a pointer */
+  std::memcpy(block, buffer, 64);
+
+  /* Copy context->state[] to working vars */
+  a = state[0];
+  b = state[1];
+  c = state[2];
+  d = state[3];
+  e = state[4];
+  /* 4 rounds of 20 operations each. Loop unrolled. */
+  R0(a, b, c, d, e, 0); R0(e, a, b, c, d, 1); R0(d, e, a, b, c, 2); R0(c, d, e, a, b, 3);
+  R0(b, c, d, e, a, 4); R0(a, b, c, d, e, 5); R0(e, a, b, c, d, 6); R0(d, e, a, b, c, 7);
+  R0(c, d, e, a, b, 8); R0(b, c, d, e, a, 9); R0(a, b, c, d, e, 10); R0(e, a, b, c, d, 11);
+  R0(d, e, a, b, c, 12); R0(c, d, e, a, b, 13); R0(b, c, d, e, a, 14); R0(a, b, c, d, e, 15);
+  R1(e, a, b, c, d, 16); R1(d, e, a, b, c, 17); R1(c, d, e, a, b, 18); R1(b, c, d, e, a, 19);
+  R2(a, b, c, d, e, 20); R2(e, a, b, c, d, 21); R2(d, e, a, b, c, 22); R2(c, d, e, a, b, 23);
+  R2(b, c, d, e, a, 24); R2(a, b, c, d, e, 25); R2(e, a, b, c, d, 26); R2(d, e, a, b, c, 27);
+  R2(c, d, e, a, b, 28); R2(b, c, d, e, a, 29); R2(a, b, c, d, e, 30); R2(e, a, b, c, d, 31);
+  R2(d, e, a, b, c, 32); R2(c, d, e, a, b, 33); R2(b, c, d, e, a, 34); R2(a, b, c, d, e, 35);
+  R2(e, a, b, c, d, 36); R2(d, e, a, b, c, 37); R2(c, d, e, a, b, 38); R2(b, c, d, e, a, 39);
+  R3(a, b, c, d, e, 40); R3(e, a, b, c, d, 41); R3(d, e, a, b, c, 42); R3(c, d, e, a, b, 43);
+  R3(b, c, d, e, a, 44); R3(a, b, c, d, e, 45); R3(e, a, b, c, d, 46); R3(d, e, a, b, c, 47);
+  R3(c, d, e, a, b, 48); R3(b, c, d, e, a, 49); R3(a, b, c, d, e, 50); R3(e, a, b, c, d, 51);
+  R3(d, e, a, b, c, 52); R3(c, d, e, a, b, 53); R3(b, c, d, e, a, 54); R3(a, b, c, d, e, 55);
+  R3(e, a, b, c, d, 56); R3(d, e, a, b, c, 57); R3(c, d, e, a, b, 58); R3(b, c, d, e, a, 59);
+  R4(a, b, c, d, e, 60); R4(e, a, b, c, d, 61); R4(d, e, a, b, c, 62); R4(c, d, e, a, b, 63);
+  R4(b, c, d, e, a, 64); R4(a, b, c, d, e, 65); R4(e, a, b, c, d, 66); R4(d, e, a, b, c, 67);
+  R4(c, d, e, a, b, 68); R4(b, c, d, e, a, 69); R4(a, b, c, d, e, 70); R4(e, a, b, c, d, 71);
+  R4(d, e, a, b, c, 72); R4(c, d, e, a, b, 73); R4(b, c, d, e, a, 74); R4(a, b, c, d, e, 75);
+  R4(e, a, b, c, d, 76); R4(d, e, a, b, c, 77); R4(c, d, e, a, b, 78); R4(b, c, d, e, a, 79);
+  /* Add the working vars back into context.state[] */
+  state[0] += a;
+  state[1] += b;
+  state[2] += c;
+  state[3] += d;
+  state[4] += e;
+}
+
+SHA1Digest::SHA1Digest()
+{
+  Reset();
+}
+
+/* SHA1Init - Initialize new context */
+
+void SHA1Digest::Reset()
+{
+  /* SHA1 initialization constants */
+  state[0] = 0x67452301;
+  state[1] = 0xEFCDAB89;
+  state[2] = 0x98BADCFE;
+  state[3] = 0x10325476;
+  state[4] = 0xC3D2E1F0;
+  count[0] = count[1] = 0;
+}
+
+std::string SHA1Digest::DigestToString(const u8 digest[20])
+{
+  std::string ret;
+  ret.reserve(DIGEST_SIZE * 2);
+  for (u32 i = 0; i < DIGEST_SIZE; i++)
+  {
+    u8 nibble = digest[i] >> 4;
+    if (nibble >= 0xA)
+      ret.push_back('A' + (nibble - 0xA));
+    else
+      ret.push_back('0' + nibble);
+    nibble = digest[i] & 0xF;
+    if (nibble >= 0xA)
+      ret.push_back('A' + (nibble - 0xA));
+    else
+      ret.push_back('0' + nibble);
+  }
+  return ret;
+}
+
+/* Run your data through this. */
+
+void SHA1Digest::Update(const void* data, u32 len)
+{
+  const u8* bdata = static_cast<const u8*>(data);
+
+  u32 i;
+  u32 j = count[0];
+  if ((count[0] += len << 3) < j)
+    count[1]++;
+  count[1] += (len >> 29);
+  j = (j >> 3) & 63;
+  if ((j + len) > 63)
+  {
+    std::memcpy(&buffer[j], bdata, (i = 64 - j));
+    SHA1Transform(state, buffer);
+    for (; i + 63 < len; i += 64)
+    {
+      SHA1Transform(state, &bdata[i]);
+    }
+    j = 0;
+  }
+  else
+  {
+    i = 0;
+  }
+  memcpy(&buffer[j], &bdata[i], len - i);
+}
+
+/* Add padding and return the message digest. */
+
+void SHA1Digest::Final(u8 digest[DIGEST_SIZE])
+{
+  u8 finalcount[8];
+  u8 c;
+
+  for (u32 i = 0; i < 8; i++)
+  {
+    finalcount[i] = (u8)((count[(i >= 4 ? 0 : 1)] >> ((3 - (i & 3)) * 8)) & 255); /* Endian independent */
+  }
+
+  c = 0200;
+  Update(&c, 1);
+  while ((count[0] & 504) != 448)
+  {
+    c = 0000;
+    Update(&c, 1);
+  }
+  Update(finalcount, 8); /* Should cause a SHA1Transform() */
+  for (u32 i = 0; i < 20; i++)
+  {
+    digest[i] = (u8)((state[i >> 2] >> ((3 - (i & 3)) * 8)) & 255);
+  }
+}
diff --git a/src/common/sha1_digest.h b/src/common/sha1_digest.h
new file mode 100644
index 000000000..a1ce01a89
--- /dev/null
+++ b/src/common/sha1_digest.h
@@ -0,0 +1,25 @@
+#pragma once
+#include "types.h"
+#include <string>
+
+class SHA1Digest
+{
+public:
+  enum : u32
+  {
+    DIGEST_SIZE = 20
+  };
+
+  SHA1Digest();
+
+  void Update(const void* data, u32 len);
+  void Final(u8 digest[DIGEST_SIZE]);
+  void Reset();
+
+  static std::string DigestToString(const u8 digest[DIGEST_SIZE]);
+
+private:
+  u32 state[5];
+  u32 count[2];
+  u8 buffer[64];
+};