diff --git a/compiler/extccomp.nim b/compiler/extccomp.nim
index db6057b5e8..2ddb98abab 100644
--- a/compiler/extccomp.nim
+++ b/compiler/extccomp.nim
@@ -585,13 +585,11 @@ proc externalFileChanged(filename: string): bool =
     return false
 
   var crcFile = toGeneratedFile(filename.withPackageName, "crc")
-  var currentCrc = int(footprint(filename))
+  var currentCrc = footprint(filename)
   var f: File
   if open(f, crcFile, fmRead):
-    var line = newStringOfCap(40)
-    if not f.readLine(line): line = "0"
+    let oldCrc = parseSecureHash(f.readLine())
     close(f)
-    var oldCrc = parseInt(line)
     result = oldCrc != currentCrc
   else:
     result = true
diff --git a/compiler/rodread.nim b/compiler/rodread.nim
index 51d60f5b54..27cb96ca14 100644
--- a/compiler/rodread.nim
+++ b/compiler/rodread.nim
@@ -541,7 +541,8 @@ proc cmdChangeTriggersRecompilation(old, new: TCommands): bool =
 proc processRodFile(r: PRodReader, crc: SecureHash) = 
   var 
     w: string
-    d, inclCrc: int
+    d: int
+  var inclCrc: SecureHash
   while r.s[r.pos] != '\0': 
     var section = rdWord(r)
     if r.reason != rrNone: 
@@ -549,7 +550,8 @@ proc processRodFile(r: PRodReader, crc: SecureHash) =
     case section 
     of "CRC": 
       inc(r.pos)              # skip ':'
-      if int(crc) != decodeVInt(r.s, r.pos): r.reason = rrCrcChange
+      if crc != parseSecureHash(decodeStr(r.s, r.pos)):
+        r.reason = rrCrcChange
     of "ID": 
       inc(r.pos)              # skip ':'
       r.moduleID = decodeVInt(r.s, r.pos)
@@ -596,9 +598,9 @@ proc processRodFile(r: PRodReader, crc: SecureHash) =
       while r.s[r.pos] != ')': 
         w = r.files[decodeVInt(r.s, r.pos)].toFullPath
         inc(r.pos)            # skip ' '
-        inclCrc = decodeVInt(r.s, r.pos)
+        inclCrc = parseSecureHash(decodeStr(r.s, r.pos))
         if r.reason == rrNone: 
-          if not existsFile(w) or (inclCrc != int(secureHashFile(w))): 
+          if not existsFile(w) or (inclCrc != secureHashFile(w)): 
             r.reason = rrInclDeps
         if r.s[r.pos] == '\x0A': 
           inc(r.pos)
@@ -649,7 +651,7 @@ proc startsWith(buf: cstring, token: string, pos = 0): bool =
   while s < token.len and buf[pos+s] == token[s]: inc s
   result = s == token.len
 
-proc newRodReader(modfilename: string, crc: SecureHash, 
+proc newRodReader(modfilename: string, crc: SecureHash,
                   readerIndex: int): PRodReader = 
   new(result)
   try:
@@ -1017,7 +1019,7 @@ proc writeType(f: File; t: PType) =
   f.write("]\n")
 
 proc viewFile(rodfile: string) =
-  var r = newRodReader(rodfile, 0, 0)
+  var r = newRodReader(rodfile, secureHash(""), 0)
   if r == nil:
     rawMessage(errGenerated, "cannot open file (or maybe wrong version):" &
        rodfile)
diff --git a/compiler/rodwrite.nim b/compiler/rodwrite.nim
index 22ecdd8af7..3454b9ade6 100644
--- a/compiler/rodwrite.nim
+++ b/compiler/rodwrite.nim
@@ -96,7 +96,7 @@ proc addInclDep(w: PRodWriter, dep: string) =
   var resolved = dep.findModule(w.module.info.toFullPath)
   encodeVInt(fileIdx(w, dep), w.inclDeps)
   add(w.inclDeps, " ")
-  encodeVInt(secureHashFile(resolved), w.inclDeps)
+  encodeStr($secureHashFile(resolved), w.inclDeps)
   add(w.inclDeps, rodNL)
 
 proc pushType(w: PRodWriter, t: PType) =
@@ -440,7 +440,7 @@ proc writeRod(w: PRodWriter) =
   f.write(rodNL)
   
   var crc = "CRC:"
-  encodeVInt(w.crc, crc)
+  encodeStr($w.crc, crc)
   f.write(crc)
   f.write(rodNL)
   
diff --git a/compiler/secure_hash.nim b/compiler/secure_hash.nim
index 7a2b6e4c20..a2ddd02f0a 100644
--- a/compiler/secure_hash.nim
+++ b/compiler/secure_hash.nim
@@ -1,101 +1,202 @@
 #
 #
 #           The Nim Compiler
-#        (c) Copyright 2012 Andreas Rumpf
+#        (c) Copyright 2015 Nim Contributers
 #
 #    See the file "copying.txt", included in this
 #    distribution, for details about the copyright.
 #
 
-import 
-  strutils
+import
+  strutils, unsigned
 
-type 
-  SecureHash* = int32
+const sha_digest_size = 20
 
-const 
-  InitCrc32 = SecureHash(- 1)
+type
+  SHA1Digest = array[0 .. sha_digest_size-1, uint8]
+  SecureHash* = distinct SHA1Digest
 
-proc secureHashFile*(filename: string): SecureHash
-# implementation
+const emptySecureHash = SecureHash([
+  0u8, 0, 0, 0,
+  0, 0, 0, 0,
+  0, 0, 0, 0,
+  0, 0, 0, 0,
+  0, 0, 0, 0,
+])
 
-type 
-  TCRC_TabEntry = int
+proc sha1(src: string) : SHA1Digest
 
-const 
-  crc32table: array[0..255, TCRC_TabEntry] = [0, 1996959894, - 301047508, 
-    - 1727442502, 124634137, 1886057615, - 379345611, - 1637575261, 249268274, 
-    2044508324, - 522852066, - 1747789432, 162941995, 2125561021, - 407360249, 
-    - 1866523247, 498536548, 1789927666, - 205950648, - 2067906082, 450548861, 
-    1843258603, - 187386543, - 2083289657, 325883990, 1684777152, - 43845254, 
-    - 1973040660, 335633487, 1661365465, - 99664541, - 1928851979, 997073096, 
-    1281953886, - 715111964, - 1570279054, 1006888145, 1258607687, - 770865667, 
-    - 1526024853, 901097722, 1119000684, - 608450090, - 1396901568, 853044451, 
-    1172266101, - 589951537, - 1412350631, 651767980, 1373503546, - 925412992, 
-    - 1076862698, 565507253, 1454621731, - 809855591, - 1195530993, 671266974, 
-    1594198024, - 972236366, - 1324619484, 795835527, 1483230225, - 1050600021, 
-    - 1234817731, 1994146192, 31158534, - 1731059524, - 271249366, 1907459465, 
-    112637215, - 1614814043, - 390540237, 2013776290, 251722036, - 1777751922, 
-    - 519137256, 2137656763, 141376813, - 1855689577, - 429695999, 1802195444, 
-    476864866, - 2056965928, - 228458418, 1812370925, 453092731, - 2113342271, 
-    - 183516073, 1706088902, 314042704, - 1950435094, - 54949764, 1658658271, 
-    366619977, - 1932296973, - 69972891, 1303535960, 984961486, - 1547960204, 
-    - 725929758, 1256170817, 1037604311, - 1529756563, - 740887301, 1131014506, 
-    879679996, - 1385723834, - 631195440, 1141124467, 855842277, - 1442165665, 
-    - 586318647, 1342533948, 654459306, - 1106571248, - 921952122, 1466479909, 
-    544179635, - 1184443383, - 832445281, 1591671054, 702138776, - 1328506846, 
-    - 942167884, 1504918807, 783551873, - 1212326853, - 1061524307, - 306674912, 
-    - 1698712650, 62317068, 1957810842, - 355121351, - 1647151185, 81470997, 
-    1943803523, - 480048366, - 1805370492, 225274430, 2053790376, - 468791541, 
-    - 1828061283, 167816743, 2097651377, - 267414716, - 2029476910, 503444072, 
-    1762050814, - 144550051, - 2140837941, 426522225, 1852507879, - 19653770, 
-    - 1982649376, 282753626, 1742555852, - 105259153, - 1900089351, 397917763, 
-    1622183637, - 690576408, - 1580100738, 953729732, 1340076626, - 776247311, 
-    - 1497606297, 1068828381, 1219638859, - 670225446, - 1358292148, 906185462, 
-    1090812512, - 547295293, - 1469587627, 829329135, 1181335161, - 882789492, 
-    - 1134132454, 628085408, 1382605366, - 871598187, - 1156888829, 570562233, 
-    1426400815, - 977650754, - 1296233688, 733239954, 1555261956, - 1026031705, 
-    - 1244606671, 752459403, 1541320221, - 1687895376, - 328994266, 1969922972, 
-    40735498, - 1677130071, - 351390145, 1913087877, 83908371, - 1782625662, 
-    - 491226604, 2075208622, 213261112, - 1831694693, - 438977011, 2094854071, 
-    198958881, - 2032938284, - 237706686, 1759359992, 534414190, - 2118248755, 
-    - 155638181, 1873836001, 414664567, - 2012718362, - 15766928, 1711684554, 
-    285281116, - 1889165569, - 127750551, 1634467795, 376229701, - 1609899400, 
-    - 686959890, 1308918612, 956543938, - 1486412191, - 799009033, 1231636301, 
-    1047427035, - 1362007478, - 640263460, 1088359270, 936918000, - 1447252397, 
-    - 558129467, 1202900863, 817233897, - 1111625188, - 893730166, 1404277552, 
-    615818150, - 1160759803, - 841546093, 1423857449, 601450431, - 1285129682, 
-    - 1000256840, 1567103746, 711928724, - 1274298825, - 1022587231, 1510334235, 
-    755167117]
+proc secureHash*(str: string): SecureHash = SecureHash(sha1(str))
+proc secureHashFile*(filename: string): SecureHash = secureHash(readFile(filename))
+proc `$`*(self: SecureHash): string =
+  result = ""
+  for v in SHA1Digest(self):
+    result.add(toHex(int(v), 2))
 
-proc updateCrc32(val: int8, crc: SecureHash): SecureHash = 
-  result = SecureHash(crc32table[(int(crc) xor (int(val) and 0x000000FF)) and
-      0x000000FF]) xor (crc shr SecureHash(8))
+proc parseSecureHash*(hash: string): SecureHash =
+  for i in 0.. <sha_digest_size:
+    SHA1Digest(result)[i] = uint8(parseHexInt(hash[i*2] & hash[i*2 + 1]))
 
-proc updateCrc32(val: char, crc: SecureHash): SecureHash = 
-  result = updateCrc32(toU8(ord(val)), crc)
+proc `==`*(a, b: SecureHash): bool =
+  # Not a constant-time comparison, but that's acceptable in this context
+  SHA1Digest(a) == SHA1Digest(b)
 
-proc secureHash*(s: string): SecureHash = 
-  result = InitCrc32
-  for i in 0..len(s)-1: result = updateCrc32(s[i], result)  
-  
-type 
-  TByteArray = array[0..10000000, int8]
-  PByteArray = ref TByteArray
 
-proc secureHashFile(filename: string): SecureHash = 
-  const 
-    bufSize = 8000 # don't use 8K for the memory allocator!
-  var 
-    bin: File
-  result = InitCrc32
-  if not open(bin, filename): 
-    return                    # not equal if file does not exist
-  var buf = alloc(bufSize)
-  var p = cast[PByteArray](buf)
-  while true: 
-    var readBytes = readBuffer(bin, buf, bufSize)
-    for i in countup(0, readBytes - 1): result = updateCrc32(p[i], result)
-    if readBytes != bufSize: break 
-  dealloc(buf)
-  close(bin)
+
+# Copyright (c) 2011, Micael Hildenborg
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+# * Redistributions of source code must retain the above copyright
+#   notice, this list of conditions and the following disclaimer.
+# * Redistributions in binary form must reproduce the above copyright
+#   notice, this list of conditions and the following disclaimer in the
+#   documentation and/or other materials provided with the distribution.
+# * Neither the name of Micael Hildenborg nor the
+#   names of its contributors may be used to endorse or promote products
+#   derived from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY Micael Hildenborg ''AS IS'' AND ANY
+# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+# DISCLAIMED. IN NO EVENT SHALL Micael Hildenborg BE LIABLE FOR ANY
+# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+# Ported to Nim by Erik O'Leary
+
+type
+  SHA1State = array[0 .. 5-1, uint32]
+  SHA1Buffer = array[0 .. 80-1, uint32]
+
+template clearBuffer(w: SHA1Buffer, len = 16) =
+  zeroMem(addr(w), len * sizeof(uint32))
+
+proc init(result: var SHA1State) =
+  result[0] = 0x67452301'u32
+  result[1] = 0xefcdab89'u32
+  result[2] = 0x98badcfe'u32
+  result[3] = 0x10325476'u32
+  result[4] = 0xc3d2e1f0'u32
+
+proc innerHash(state: var SHA1State, w: var SHA1Buffer) =
+  var
+    a = state[0]
+    b = state[1]
+    c = state[2]
+    d = state[3]
+    e = state[4]
+
+  var round = 0
+
+  template rot(value, bits: uint32): uint32 {.immediate.} =
+    (value shl bits) or (value shr (32 - bits))
+
+  template sha1(fun, val: uint32): stmt =
+    let t = rot(a, 5) + fun + e + val + w[round]
+    e = d
+    d = c
+    c = rot(b, 30)
+    b = a
+    a = t
+
+  template process(body: stmt): stmt =
+    w[round] = rot(w[round - 3] xor w[round - 8] xor w[round - 14] xor w[round - 16], 1)
+    body
+    inc(round)
+
+  template wrap(dest, value: expr): stmt {.immediate.} =
+    let v = dest + value
+    dest = v
+
+  while round < 16:
+    sha1((b and c) or (not b and d), 0x5a827999'u32)
+    inc(round)
+
+  while round < 20:
+    process:
+      sha1((b and c) or (not b and d), 0x5a827999'u32)
+
+  while round < 40:
+    process:
+      sha1(b xor c xor d, 0x6ed9eba1'u32)
+
+  while round < 60:
+    process:
+      sha1((b and c) or (b and d) or (c and d), 0x8f1bbcdc'u32)
+
+  while round < 80:
+    process:
+      sha1(b xor c xor d, 0xca62c1d6'u32)
+
+  wrap state[0], a
+  wrap state[1], b
+  wrap state[2], c
+  wrap state[3], d
+  wrap state[4], e
+
+template computeInternal(src: expr): stmt {.immediate.} =
+  #Initialize state
+  var state: SHA1State
+  init(state)
+
+  #Create w buffer
+  var w: SHA1Buffer
+
+  #Loop through all complete 64byte blocks.
+  let byteLen         = src.len
+  let endOfFullBlocks = byteLen - 64
+  var endCurrentBlock = 0
+  var currentBlock    = 0
+
+  while currentBlock <= endOfFullBlocks:
+    endCurrentBlock = currentBlock + 64
+
+    var i = 0
+    while currentBlock < endCurrentBlock:
+      w[i] = uint32(src[currentBlock+3]) or
+             uint32(src[currentBlock+2]) shl 8'u32 or
+             uint32(src[currentBlock+1]) shl 16'u32 or
+             uint32(src[currentBlock])   shl 24'u32
+      currentBlock += 4
+      inc(i)
+
+    innerHash(state, w)
+
+  #Handle last and not full 64 byte block if existing
+  endCurrentBlock = byteLen - currentBlock
+  clearBuffer(w)
+  var lastBlockBytes = 0
+
+  while lastBlockBytes < endCurrentBlock:
+
+    var value = uint32(src[lastBlockBytes + currentBlock]) shl
+                ((3'u32 - (lastBlockBytes and 3)) shl 3)
+
+    w[lastBlockBytes shr 2] = w[lastBlockBytes shr 2] or value
+    inc(lastBlockBytes)
+
+  w[lastBlockBytes shr 2] = w[lastBlockBytes shr 2] or (
+    0x80'u32 shl ((3'u32 - (lastBlockBytes and 3)) shl 3)
+  )
+
+  if endCurrentBlock >= 56:
+    innerHash(state, w)
+    clearBuffer(w)
+
+  w[15] = uint32(byteLen) shl 3
+  innerHash(state, w)
+
+  # Store hash in result pointer, and make sure we get in in the correct order
+  # on both endian models.
+  for i in 0 .. sha_digest_size-1:
+    result[i] = uint8((int(state[i shr 2]) shr ((3-(i and 3)) * 8)) and 255)
+
+proc sha1(src: string) : SHA1Digest =
+  ## Calculate SHA1 from input string
+  computeInternal(src)