diff --git a/Makefile.am b/Makefile.am
index 9db11916..1a05dbb6 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -7,12 +7,18 @@ AM_CXXFLAGS = $(BOOST_CPPFLAGS) $(COMMON_CXXFLAGS)
 SUBDIRS = test
 
 UTIL_FILES   =		\
+    adler.hpp		\
+    adler.cpp		\
     annotations.hpp 	\
     backtrace.hpp   	\
     bitwise.cpp		\
     bitwise.hpp		\
+    bsdsum.hpp		\
+    bsdsum.cpp		\
     colour.cpp		\
     colour.hpp		\
+    crc.cpp		\
+    crc.hpp		\
     debug.cpp   	\
     debug.hpp   	\
     enable_if.hpp  	\
@@ -24,6 +30,7 @@ UTIL_FILES   =		\
     extent.hpp		\
     fixed.cpp		\
     fixed.hpp		\
+    fletcher.hpp	\
     float.cpp		\
     float.hpp		\
     fwd.hpp		\
diff --git a/adler.cpp b/adler.cpp
new file mode 100644
index 00000000..8f844300
--- /dev/null
+++ b/adler.cpp
@@ -0,0 +1,30 @@
+/*
+ * This file is part of libgim.
+ *
+ * Waif is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ * 
+ * Waif is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with libgim.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright 2010 Danny Robson <danny@blubinc.net>
+ */
+
+#include "adler.hpp"
+
+#include "debug.hpp"
+#include "fletcher.hpp"
+
+static const unsigned MODULUS = 65521;
+
+uint32_t
+adler32 (const void* restrict _data, size_t _size)
+    { return fletcher<32, MODULUS, 1, 0> (_data, _size); }
+
diff --git a/adler.hpp b/adler.hpp
new file mode 100644
index 00000000..e76a9670
--- /dev/null
+++ b/adler.hpp
@@ -0,0 +1,28 @@
+/*
+ * This file is part of libgim.
+ *
+ * Waif is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ * 
+ * Waif is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with libgim.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright 2010 Danny Robson <danny@blubinc.net>
+ */
+
+#ifndef __UTIL_ADLER_HPP
+#define __UTIL_ADLER_HPP
+
+#include <cstdint>
+#include <cstdlib>
+
+extern uint32_t adler32(const void* restrict, size_t);
+
+#endif
diff --git a/bsdsum.cpp b/bsdsum.cpp
new file mode 100644
index 00000000..016e32fb
--- /dev/null
+++ b/bsdsum.cpp
@@ -0,0 +1,35 @@
+/*
+ * This file is part of libgim.
+ *
+ * Waif is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ * 
+ * Waif is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with libgim.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright 2010 Danny Robson <danny@blubinc.net>
+ */
+
+#include "bsdsum.hpp"
+
+
+uint16_t
+bsdsum (const void *restrict _data, size_t size) {
+    const uint8_t *restrict data = static_cast<const uint8_t*> (data);
+    uint16_t accum = 0;
+
+    for (size_t i = 0; i < size; ++i) {
+        accum  = (accum >> 1) | ((accum & 0x1) << 15);
+        accum += data[i];
+    }
+
+    return accum;
+}
+
diff --git a/bsdsum.hpp b/bsdsum.hpp
new file mode 100644
index 00000000..c1d80e51
--- /dev/null
+++ b/bsdsum.hpp
@@ -0,0 +1,28 @@
+/*
+ * This file is part of libgim.
+ *
+ * Waif is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ * 
+ * Waif is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with libgim.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright 2010 Danny Robson <danny@blubinc.net>
+ */
+
+#ifndef __UTIL_BSDSUM_HPP
+#define __UTIL_BSDSUMP_HPP
+
+#include <cstdint>
+#include <cstdlib>
+
+uint16_t bsdsum (const void *restrict, size_t);
+
+#endif
diff --git a/crc.cpp b/crc.cpp
new file mode 100644
index 00000000..8d26f0ed
--- /dev/null
+++ b/crc.cpp
@@ -0,0 +1,58 @@
+/*
+ * This file is part of libgim.
+ *
+ * libgim is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ * 
+ * libgim is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with libgim.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright 2011 Danny Robson <danny@blubinc.net>
+ */
+
+#include "crc.hpp"
+
+#include "debug.hpp"
+#include "endian.hpp"
+
+uint32_t
+crc32 (const void *restrict, size_t) {
+    not_implemented ();
+
+    /*
+    const uint8_t *restrict data = static_cast<const uint8_t*> (_data);
+    static const uint32_t POLYNOMIAL = hton (static_cast<uint32_t>(0x04C11DB7));
+
+    uint64_t bits = 0;
+    unsigned int i = 0;
+
+    if (size == 0)
+        return POLYNOMIAL;
+
+    switch (size) {
+        default:    bits |= static_cast<uint64_t>(data[3]) << 32U;
+        case 3:     bits |= static_cast<uint64_t>(data[2]) << 40U;
+        case 2:     bits |= static_cast<uint64_t>(data[1]) << 48U;
+        case 1:     bits |= static_cast<uint64_t>(data[0]) << 56U;
+    }
+    
+    for (size_t i = 0; i < size; ++i) {
+        for (unsigned j = 0; j < 32; ++j) {
+            bool mix = bits 0x7000000000000000ULL;
+            bits <<= 1;
+
+            if (mix) 
+                bits ^= POLYNOMIAL << 32;
+        }
+
+
+    }
+    */
+}
diff --git a/crc.hpp b/crc.hpp
new file mode 100644
index 00000000..f6979b12
--- /dev/null
+++ b/crc.hpp
@@ -0,0 +1,29 @@
+/*
+ * This file is part of libgim.
+ *
+ * libgim is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ * 
+ * libgim is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with libgim.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright 2011 Danny Robson <danny@blubinc.net>
+ */
+
+#ifndef __UTIL_CRC_HPP
+#define __UTIL_CRC_HPP
+
+#include <cstdint>
+#include <cstdlib>
+
+uint32_t crc32 (const void *restrict, size_t);
+
+#endif
+
diff --git a/fletcher.hpp b/fletcher.hpp
new file mode 100644
index 00000000..a63ebcaa
--- /dev/null
+++ b/fletcher.hpp
@@ -0,0 +1,44 @@
+/*
+ * This file is part of libgim.
+ *
+ * Waif is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ * 
+ * Waif is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with libgim.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright 2010 Danny Robson <danny@blubinc.net>
+ */
+
+#ifndef __UTIL_FLETCHER_HPP
+#define __UTIL_FLETCHER_HPP
+
+#include "types.hpp"
+
+#include <cstdint>
+#include <cstdlib>
+
+template <unsigned BITS, unsigned MODULUS, unsigned INITIAL_A, unsigned INITIAL_B>
+typename bits_type<BITS>::uint
+fletcher (const void *restrict _data, size_t size) {
+    const uint8_t *restrict data = static_cast<const uint8_t*> (_data);
+    typename bits_type<BITS>::uint A = INITIAL_A,
+                                   B = INITIAL_B;
+
+    for (size_t i = 0; i < size; ++i) {
+        A = (A + data[i]) % MODULUS;
+        B = (A +       B) % MODULUS;
+    }
+
+    return (B << (BITS / 2)) | A;
+}
+
+#endif
+
diff --git a/test/.gitignore b/test/.gitignore
index 90d95a58..65f608cc 100644
--- a/test/.gitignore
+++ b/test/.gitignore
@@ -1,3 +1,4 @@
+/adler
 /backtrace*
 /float*
 /hton*
diff --git a/test/Makefile.am b/test/Makefile.am
index f9b97c77..113d4bc1 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -9,6 +9,7 @@ AM_LDFLAGS  = $(COMMON_LDFLAGS)
 
 TEST_BIN = 		\
 	backtrace 	\
+	checksum	\
 	float		\
 	hton		\
 	ip 		\
@@ -27,6 +28,9 @@ backtrace_CPPFLAGS = $(COMMON_CXXFLAGS)
 backtrace_LDADD    = $(builddir)/../libutil.la
 backtrace_SOURCES  = backtrace.cpp
 
+checksum_LDADD	   = $(builddir)/../libutil.la
+checksum_SOURCES   = checksum.cpp
+
 float_LDADD        = $(builddir)/../libutil.la
 float_SOURCES      = float.cpp
 
diff --git a/test/checksum.cpp b/test/checksum.cpp
new file mode 100644
index 00000000..dbb6315c
--- /dev/null
+++ b/test/checksum.cpp
@@ -0,0 +1,32 @@
+
+#include "adler.hpp"
+#include "bsdsum.hpp"
+#include "types.hpp"
+
+#include <cstdlib>
+#include <cstring>
+
+using namespace std;
+
+static const char *ALPHABET = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+
+static const struct {
+    uint32_t adler;
+    uint16_t bsd;
+    
+    const char *data;
+    size_t      size;
+} TESTS[] = {
+    { 0xDF5B150C, 0x52FB, ALPHABET, strlen (ALPHABET) }
+};
+
+
+int
+main (int, char**) {
+    for (unsigned i = 0; i < elems (TESTS); ++i) {
+        check_eq (TESTS[i].adler, adler32 (TESTS[i].data, TESTS[i].size));
+        check_eq (TESTS[i].bsd,   bsdsum (TESTS[i].data, TESTS[i].size));
+    }
+
+    return EXIT_SUCCESS;
+}