diff --git a/CHANGELOG.md b/CHANGELOG.md
index 66a51c3..aeb4411 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,11 @@
 # Changelog
 
 
+#### 2.0.1
+
+Major performance improvements.
+
+
 #### 2.0.0
 
 The hash functions now take `Binary.Bits` instead of `String`s.
diff --git a/docs.json b/docs.json
index 0012539..4cfb4a3 100644
--- a/docs.json
+++ b/docs.json
@@ -1 +1 @@
-[{"name":"SHA","comment":" An implementation of several [SHA](https://en.wikipedia.org/wiki/Secure_Hash_Algorithms) cryptographic hash functions. This package uses [icidasset/elm-binary](https://package.elm-lang.org/packages/icidasset/elm-binary/latest/) to work with binary numbers.\n\n@docs sha224, sha256, sha384, sha512\n\n","unions":[],"aliases":[],"values":[{"name":"sha224","comment":" SHA-224.\n\n    >>> import Binary\n\n    >>> \"abc\"\n    ..>   |> Binary.fromStringAsUtf8\n    ..>   |> SHA.sha224\n    ..>   |> Binary.toHex\n    \"23097D223405D8228642A477BDA255B32AADBCE4BDA0B3F7E36C9DA7\"\n\n    >>> \"abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu\"\n    ..>   |> Binary.fromStringAsUtf8\n    ..>   |> SHA.sha224\n    ..>   |> Binary.toHex\n    \"C97CA9A559850CE97A04A96DEF6D99A9E0E0E2AB14E6B8DF265FC0B3\"\n\n","type":"Binary.Bits -> Binary.Bits"},{"name":"sha256","comment":" SHA-256.\n\n    >>> import Binary\n\n    >>> \"abc\"\n    ..>   |> Binary.fromStringAsUtf8\n    ..>   |> SHA.sha256\n    ..>   |> Binary.toHex\n    \"BA7816BF8F01CFEA414140DE5DAE2223B00361A396177A9CB410FF61F20015AD\"\n\n    >>> \"abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu\"\n    ..>   |> Binary.fromStringAsUtf8\n    ..>   |> SHA.sha256\n    ..>   |> Binary.toHex\n    \"CF5B16A778AF8380036CE59E7B0492370B249B11E8F07A51AFAC45037AFEE9D1\"\n\n","type":"Binary.Bits -> Binary.Bits"},{"name":"sha384","comment":" SHA-384.\n\n    >>> import Binary\n\n    >>> \"abc\"\n    ..>   |> Binary.fromStringAsUtf8\n    ..>   |> SHA.sha384\n    ..>   |> Binary.toHex\n    \"CB00753F45A35E8BB5A03D699AC65007272C32AB0EDED1631A8B605A43FF5BED8086072BA1E7CC2358BAECA134C825A7\"\n\n    >>> \"abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu\"\n    ..>   |> Binary.fromStringAsUtf8\n    ..>   |> SHA.sha384\n    ..>   |> Binary.toHex\n    \"09330C33F71147E83D192FC782CD1B4753111B173B3B05D22FA08086E3B0F712FCC7C71A557E2DB966C3E9FA91746039\"\n\n","type":"Binary.Bits -> Binary.Bits"},{"name":"sha512","comment":" SHA-512.\n\n    >>> import Binary\n\n    >>> \"abc\"\n    ..>   |> Binary.fromStringAsUtf8\n    ..>   |> SHA.sha512\n    ..>   |> Binary.toHex\n    \"DDAF35A193617ABACC417349AE20413112E6FA4E89A97EA20A9EEEE64B55D39A2192992A274FC1A836BA3C23A3FEEBBD454D4423643CE80E2A9AC94FA54CA49F\"\n\n    >>> \"abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu\"\n    ..>   |> Binary.fromStringAsUtf8\n    ..>   |> SHA.sha512\n    ..>   |> Binary.toHex\n    \"8E959B75DAE313DA8CF4F72814FC143F8F7779C6EB9F7FA17299AEADB6889018501D289E4900F7E4331B99DEC4B5433AC7D329EEB6DD26545E96E55B874BE909\"\n\n","type":"Binary.Bits -> Binary.Bits"}],"binops":[]}]
\ No newline at end of file
+[{"name":"SHA","comment":" An implementation of several [SHA](https://en.wikipedia.org/wiki/Secure_Hash_Algorithms) cryptographic hash functions. This package uses [icidasset/elm-binary](https://package.elm-lang.org/packages/icidasset/elm-binary/latest/) to work with binary numbers.\n\n@docs sha224, sha256, sha384, sha512\n\n","unions":[],"aliases":[],"values":[{"name":"sha224","comment":" SHA-224.\n\n    >>> import Binary\n\n    >>> \"abc\"\n    ..>   |> Binary.fromStringAsUtf8\n    ..>   |> SHA.sha224\n    ..>   |> Binary.toHex\n    \"23097D223405D8228642A477BDA255B32AADBCE4BDA0B3F7E36C9DA7\"\n\n","type":"Binary.Bits -> Binary.Bits"},{"name":"sha256","comment":" SHA-256.\n\n    >>> import Binary\n\n    >>> \"abc\"\n    ..>   |> Binary.fromStringAsUtf8\n    ..>   |> SHA.sha256\n    ..>   |> Binary.toHex\n    \"BA7816BF8F01CFEA414140DE5DAE2223B00361A396177A9CB410FF61F20015AD\"\n\n","type":"Binary.Bits -> Binary.Bits"},{"name":"sha384","comment":" SHA-384.\n\n    >>> import Binary\n\n    >>> \"abc\"\n    ..>   |> Binary.fromStringAsUtf8\n    ..>   |> SHA.sha384\n    ..>   |> Binary.toHex\n    \"CB00753F45A35E8BB5A03D699AC65007272C32AB0EDED1631A8B605A43FF5BED8086072BA1E7CC2358BAECA134C825A7\"\n\n","type":"Binary.Bits -> Binary.Bits"},{"name":"sha512","comment":" SHA-512.\n\n    >>> import Binary\n\n    >>> \"abc\"\n    ..>   |> Binary.fromStringAsUtf8\n    ..>   |> SHA.sha512\n    ..>   |> Binary.toHex\n    \"DDAF35A193617ABACC417349AE20413112E6FA4E89A97EA20A9EEEE64B55D39A2192992A274FC1A836BA3C23A3FEEBBD454D4423643CE80E2A9AC94FA54CA49F\"\n\n","type":"Binary.Bits -> Binary.Bits"}],"binops":[]}]
\ No newline at end of file
diff --git a/elm.json b/elm.json
index b129768..1be4d72 100644
--- a/elm.json
+++ b/elm.json
@@ -3,7 +3,7 @@
     "name": "icidasset/elm-sha",
     "summary": "SHA cryptographic hash functions.",
     "license": "MIT",
-    "version": "2.0.0",
+    "version": "2.0.1",
     "exposed-modules": [
         "SHA"
     ],
diff --git a/src/SHA.elm b/src/SHA.elm
index edd83a0..5cb1cc8 100644
--- a/src/SHA.elm
+++ b/src/SHA.elm
@@ -25,12 +25,6 @@ import SHA.Internal.SHA512
     ..>   |> Binary.toHex
     "23097D223405D8228642A477BDA255B32AADBCE4BDA0B3F7E36C9DA7"
 
-    >>> "abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu"
-    ..>   |> Binary.fromStringAsUtf8
-    ..>   |> SHA.sha224
-    ..>   |> Binary.toHex
-    "C97CA9A559850CE97A04A96DEF6D99A9E0E0E2AB14E6B8DF265FC0B3"
-
 -}
 sha224 : Bits -> Bits
 sha224 message =
@@ -50,12 +44,6 @@ sha224 message =
     ..>   |> Binary.toHex
     "BA7816BF8F01CFEA414140DE5DAE2223B00361A396177A9CB410FF61F20015AD"
 
-    >>> "abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu"
-    ..>   |> Binary.fromStringAsUtf8
-    ..>   |> SHA.sha256
-    ..>   |> Binary.toHex
-    "CF5B16A778AF8380036CE59E7B0492370B249B11E8F07A51AFAC45037AFEE9D1"
-
 -}
 sha256 : Bits -> Bits
 sha256 message =
@@ -75,12 +63,6 @@ sha256 message =
     ..>   |> Binary.toHex
     "CB00753F45A35E8BB5A03D699AC65007272C32AB0EDED1631A8B605A43FF5BED8086072BA1E7CC2358BAECA134C825A7"
 
-    >>> "abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu"
-    ..>   |> Binary.fromStringAsUtf8
-    ..>   |> SHA.sha384
-    ..>   |> Binary.toHex
-    "09330C33F71147E83D192FC782CD1B4753111B173B3B05D22FA08086E3B0F712FCC7C71A557E2DB966C3E9FA91746039"
-
 -}
 sha384 : Bits -> Bits
 sha384 message =
@@ -100,12 +82,6 @@ sha384 message =
     ..>   |> Binary.toHex
     "DDAF35A193617ABACC417349AE20413112E6FA4E89A97EA20A9EEEE64B55D39A2192992A274FC1A836BA3C23A3FEEBBD454D4423643CE80E2A9AC94FA54CA49F"
 
-    >>> "abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu"
-    ..>   |> Binary.fromStringAsUtf8
-    ..>   |> SHA.sha512
-    ..>   |> Binary.toHex
-    "8E959B75DAE313DA8CF4F72814FC143F8F7779C6EB9F7FA17299AEADB6889018501D289E4900F7E4331B99DEC4B5433AC7D329EEB6DD26545E96E55B874BE909"
-
 -}
 sha512 : Bits -> Bits
 sha512 message =
diff --git a/src/SHA/Internal/Common.elm b/src/SHA/Internal/Common.elm
index c778342..b6f1fcf 100644
--- a/src/SHA/Internal/Common.elm
+++ b/src/SHA/Internal/Common.elm
@@ -59,9 +59,10 @@ combine sizeInBits x y =
                 width - sizeInBits
         in
         -- Is the sum larger than the modulo constant (ie. 2 ^ sizeInBits)?
-        (True :: List.repeat (sizeInBits + excess - 1) False)
+        sum
+            |> Binary.toBooleans
+            |> List.drop excess
             |> Binary.fromBooleans
-            |> Binary.subtract sum
             |> Binary.dropLeadingZeros
             |> Binary.ensureSize sizeInBits
 
diff --git a/src/SHA/Internal/Tests.elm b/src/SHA/Internal/Tests.elm
new file mode 100644
index 0000000..5004d30
--- /dev/null
+++ b/src/SHA/Internal/Tests.elm
@@ -0,0 +1,113 @@
+module SHA.Internal.Tests exposing (sha224, sha256, sha384, sha512)
+
+{-| Tests.
+
+    >>> import Binary
+
+-}
+
+import SHA
+
+
+{-| SHA-224 tests.
+
+    >>> "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"
+    ..>   |> Binary.fromStringAsUtf8
+    ..>   |> sha224
+    ..>   |> Binary.toHex
+    "75388B16512776CC5DBA5DA1FD890150B0C6455CB4F58B1952522525"
+
+    >>> "abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu"
+    ..>   |> Binary.fromStringAsUtf8
+    ..>   |> sha224
+    ..>   |> Binary.toHex
+    "C97CA9A559850CE97A04A96DEF6D99A9E0E0E2AB14E6B8DF265FC0B3"
+
+    >>> "a"
+    ..>   |> String.repeat 10000
+    ..>   |> Binary.fromStringAsUtf8
+    ..>   |> sha224
+    ..>   |> Binary.toHex
+    "00568FBA93E8718C2F7DCD82FA94501D59BB1BBCBA2C7DC2BA5882DB"
+
+-}
+sha224 =
+    SHA.sha224
+
+
+{-| SHA-256 tests.
+
+    >>> "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"
+    ..>   |> Binary.fromStringAsUtf8
+    ..>   |> sha256
+    ..>   |> Binary.toHex
+    "248D6A61D20638B8E5C026930C3E6039A33CE45964FF2167F6ECEDD419DB06C1"
+
+    >>> "abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu"
+    ..>   |> Binary.fromStringAsUtf8
+    ..>   |> sha256
+    ..>   |> Binary.toHex
+    "CF5B16A778AF8380036CE59E7B0492370B249B11E8F07A51AFAC45037AFEE9D1"
+
+    >>> "a"
+    ..>   |> String.repeat 10000
+    ..>   |> Binary.fromStringAsUtf8
+    ..>   |> sha256
+    ..>   |> Binary.toHex
+    "27DD1F61B867B6A0F6E9D8A41C43231DE52107E53AE424DE8F847B821DB4B711"
+
+-}
+sha256 =
+    SHA.sha256
+
+
+{-| SHA-384 tests.
+
+    >>> "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"
+    ..>   |> Binary.fromStringAsUtf8
+    ..>   |> sha384
+    ..>   |> Binary.toHex
+    "3391FDDDFC8DC7393707A65B1B4709397CF8B1D162AF05ABFE8F450DE5F36BC6B0455A8520BC4E6F5FE95B1FE3C8452B"
+
+    >>> "abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu"
+    ..>   |> Binary.fromStringAsUtf8
+    ..>   |> sha384
+    ..>   |> Binary.toHex
+    "09330C33F71147E83D192FC782CD1B4753111B173B3B05D22FA08086E3B0F712FCC7C71A557E2DB966C3E9FA91746039"
+
+    >>> "a"
+    ..>   |> String.repeat 10000
+    ..>   |> Binary.fromStringAsUtf8
+    ..>   |> sha384
+    ..>   |> Binary.toHex
+    "2BCA3B131BB7E922BCD1DE98C44786D32E6B6B2993E69C4987EDF9DD49711EB501F0E98AD248D839F6BF9E116E25A97C"
+
+-}
+sha384 =
+    SHA.sha384
+
+
+{-| SHA-512 tests.
+
+    >>> "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"
+    ..>   |> Binary.fromStringAsUtf8
+    ..>   |> sha512
+    ..>   |> Binary.toHex
+    "204A8FC6DDA82F0A0CED7BEB8E08A41657C16EF468B228A8279BE331A703C33596FD15C13B1B07F9AA1D3BEA57789CA031AD85C7A71DD70354EC631238CA3445"
+
+    >>> "abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu"
+    ..>   |> Binary.fromStringAsUtf8
+    ..>   |> sha512
+    ..>   |> Binary.toHex
+    "8E959B75DAE313DA8CF4F72814FC143F8F7779C6EB9F7FA17299AEADB6889018501D289E4900F7E4331B99DEC4B5433AC7D329EEB6DD26545E96E55B874BE909"
+
+    >>> "a"
+    ..>   |> String.repeat 10000
+    ..>   |> Binary.fromStringAsUtf8
+    ..>   |> sha512
+    ..>   |> Binary.toHex
+    "0593036F4F479D2EB8078CA26B1D59321A86BDFCB04CB40043694F1EB0301B8ACD20B936DB3C916EBCC1B609400FFCF3FA8D569D7E39293855668645094BAF0E"
+
+-}
+sha512 =
+    SHA.sha512