diff --git a/README.md b/README.md
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--- /dev/null
+++ b/README.md
@@ -0,0 +1,7 @@
+# tblyler/go-mcrypt
+
+This is a work in progress and currently just implements an encrypt and decrypt function that is compliant with PHP's rijndael AES 256 specification.
+As one might guess, this was to replace existing PHP code that relied on rijndael AES 256.
+
+## Requirements
+ * libmcrypt
diff --git a/mcrypt.go b/mcrypt.go
new file mode 100644
index 0000000..2d962b0
--- /dev/null
+++ b/mcrypt.go
@@ -0,0 +1,253 @@
+package mcrypt
+
+/*
+#cgo LDFLAGS: -lmcrypt
+#include <stdlib.h>
+#include <string.h>
+#include <mcrypt.h>
+
+#define FAILED_MCRYPT_MODULE 1
+#define INVALID_KEY_LENGTH 2
+#define INVALID_IV_LENGTH 3
+#define FAILED_TO_ENCRYPT_DATA 4
+#define FAILED_TO_DECRYPT_DATA 5
+#define INVALID_DATA_LENGTH 6
+
+// getError convert a given error code to its string representation
+const char* getError(int err) {
+	switch (err) {
+	case FAILED_MCRYPT_MODULE:
+		return "Failed to open mcrypt module";
+
+	case INVALID_KEY_LENGTH:
+		return "Invalid key length";
+
+	case INVALID_IV_LENGTH:
+		return "Invalid iv length";
+
+	case FAILED_TO_ENCRYPT_DATA:
+		return "Failed to encrypt data";
+
+	case FAILED_TO_DECRYPT_DATA:
+		return "Failed to decrypt data";
+
+	case INVALID_DATA_LENGTH:
+		return "Invalid data length";
+	}
+
+	return mcrypt_strerror(err);
+}
+
+// encrypt encrypt a given data set with rijndael 256
+char* encrypt(void* key, int keyLength, void* iv, int ivLength, char* data, int* length, int* err) {
+	if (*length <= 0) {
+		*err = INVALID_DATA_LENGTH;
+		return NULL;
+	}
+
+	int i;
+
+	MCRYPT td = mcrypt_module_open("rijndael-256", NULL, "cbc", NULL);
+	if (td == MCRYPT_FAILED) {
+		*err = FAILED_MCRYPT_MODULE;
+		return NULL;
+	}
+
+	int requiredKeySize = mcrypt_enc_get_key_size(td);
+	int requiredIvSize = mcrypt_enc_get_iv_size(td);
+
+	// make sure the key and iv are the correct sizes
+	if (keyLength != requiredKeySize) {
+		*err = INVALID_KEY_LENGTH;
+		mcrypt_module_close(td);
+		return NULL;
+	}
+
+	if (ivLength != requiredIvSize) {
+		*err = INVALID_IV_LENGTH;
+		mcrypt_module_close(td);
+		return NULL;
+	}
+
+	*err = mcrypt_generic_init(td, key, keyLength, iv);
+	if (*err) {
+		mcrypt_generic_deinit(td);
+		mcrypt_module_close(td);
+		return NULL;
+	}
+
+	// get the block size
+	int blockSize = mcrypt_enc_get_block_size(td);
+
+	// determine the new length if needed
+	int newLength = 0;
+
+	// if blockSize is greater than length, expand length to the blockSize
+	if (blockSize > *length) {
+		newLength = blockSize;
+	} else {
+		int lengthBlockMod = *length % blockSize;
+		if (lengthBlockMod) {
+			// if length is not multiple of blockSize, make it the next highest blockSize
+			newLength = *length - lengthBlockMod + blockSize;
+		} else {
+			// we do not need to change the length
+			newLength = *length;
+		}
+	}
+
+	// allocate and copy the data to the output value
+	char* output = malloc(sizeof *output * newLength);
+	// append byte zeroes to the output array if needed
+	for (i = *length; i < newLength; ++i) {
+		output[i] = 0;
+	}
+
+	memcpy(output, data, *length);
+
+	// update the length to the reallocated length
+	*length = newLength;
+
+	// loop through the output data by blockSize at a time
+	for (i = 0; i < *length; i += blockSize) {
+		// encrypt the block of output[i] plus blockSize
+		if (mcrypt_generic(td, output+i, blockSize)) {
+			*err = FAILED_TO_ENCRYPT_DATA;
+			mcrypt_generic_deinit(td);
+			mcrypt_module_close(td);
+			free(output);
+			return NULL;
+		}
+	}
+
+	// finish up mcrypt
+	mcrypt_generic_deinit(td);
+	mcrypt_module_close(td);
+
+	// return the encrypted data
+	return output;
+}
+
+// decrypt decrypt a given data set with rijndael 256
+char* decrypt(void* key, int keyLength, void* iv, int ivLength, char* data, int* length, int* err) {
+	int i;
+
+	MCRYPT td = mcrypt_module_open("rijndael-256", NULL, "cbc", NULL);
+	if (td == MCRYPT_FAILED) {
+		*err = FAILED_MCRYPT_MODULE;
+		mcrypt_module_close(td);
+		return NULL;
+	}
+
+	int requiredKeySize = mcrypt_enc_get_key_size(td);
+	int requiredIvSize = mcrypt_enc_get_iv_size(td);
+
+	// make sure the key and iv are the correct sizes
+	if (keyLength != requiredKeySize) {
+		*err = INVALID_KEY_LENGTH;
+		mcrypt_module_close(td);
+		return NULL;
+	}
+
+	if (ivLength != requiredIvSize) {
+		*err = INVALID_IV_LENGTH;
+		mcrypt_module_close(td);
+		return NULL;
+	}
+
+	*err = mcrypt_generic_init(td, key, keyLength, iv);
+	if (*err) {
+		mcrypt_generic_deinit(td);
+		mcrypt_module_close(td);
+		return NULL;
+	}
+
+	// get the block size
+	int blockSize = mcrypt_enc_get_block_size(td);
+
+	if (*length < blockSize || *length % blockSize) {
+		*err = INVALID_DATA_LENGTH;
+		mcrypt_generic_deinit(td);
+		mcrypt_module_close(td);
+		return NULL;
+	}
+
+	// allocate and copy the data to the output value
+	char* output = malloc(sizeof *output * *length);
+
+	memcpy(output, data, *length);
+
+	// loop through the output data by blockSize at a time
+	for (i = 0; i < *length; i += blockSize) {
+		// decrypt the block of output[i] plus blockSize
+		if (mdecrypt_generic(td, output+i, blockSize)) {
+			*err = FAILED_TO_DECRYPT_DATA;
+			mcrypt_generic_deinit(td);
+			mcrypt_module_close(td);
+			free(output);
+			return NULL;
+		}
+	}
+
+	// finish up mcrypt
+	mcrypt_generic_deinit(td);
+	mcrypt_module_close(td);
+
+	// return the decrypted data
+	return output;
+}
+*/
+import "C"
+
+import (
+	"errors"
+	"unsafe"
+)
+
+// Encrypt encrypt something with mcrypt rijndael-256 PHP-style
+func Encrypt(key []byte, iv []byte, data []byte) ([]byte, error) {
+	// keep track of the size of the input data
+	length := C.int(len(data))
+	if length == 0 {
+		return nil, errors.New("Invalid data size of 0")
+	}
+	// keep track of any errors that occur on encryption
+	err := C.int(0)
+	// encrypt the data
+	encryptedData := C.encrypt(unsafe.Pointer(&key[0]), C.int(len(key)), unsafe.Pointer(&iv[0]), C.int(len(iv)), (*C.char)(unsafe.Pointer(&data[0])), (*C.int)(unsafe.Pointer(&length)), (*C.int)(unsafe.Pointer(&err)))
+
+	// if err is not 0, there is an error
+	if int(err) != 0 {
+		return nil, errors.New(C.GoString(C.getError(err)))
+	}
+
+	// ensure that memory is freed on the encrypted data after it is converted to Go bytes
+	defer C.free(unsafe.Pointer(encryptedData))
+
+	// return the Go bytes of the encrypted data
+	return C.GoBytes(unsafe.Pointer(encryptedData), length), nil
+}
+
+// Decrypt decrypt something with mcrypt rijndael-256 PHP-style
+func Decrypt(key []byte, iv []byte, data []byte) ([]byte, error) {
+	// keep track of the size of the input data
+	length := C.int(len(data))
+	if length == 0 {
+		return nil, errors.New("Invalid data size of 0")
+	}
+	// keep track of any errors that occur on decryption
+	err := C.int(0)
+	// decrypt the data
+	decryptedData := C.decrypt(unsafe.Pointer(&key[0]), C.int(len(key)), unsafe.Pointer(&iv[0]), C.int(len(iv)), (*C.char)(unsafe.Pointer(&data[0])), (*C.int)(unsafe.Pointer(&length)), (*C.int)(unsafe.Pointer(&err)))
+
+	// if err is not 0, there is an error
+	if int(err) != 0 {
+		return nil, errors.New(C.GoString(C.getError(err)))
+	}
+
+	// ensure that memory is freed on the decrypted data after it is converted to Go bytes
+	defer C.free(unsafe.Pointer(decryptedData))
+
+	// return the Go bytes of the decrypted data
+	return C.GoBytes(unsafe.Pointer(decryptedData), length), nil
+}
diff --git a/mcrypt_test.go b/mcrypt_test.go
new file mode 100644
index 0000000..8077db5
--- /dev/null
+++ b/mcrypt_test.go
@@ -0,0 +1,153 @@
+package mcrypt
+
+import (
+	"bytes"
+	"crypto/rand"
+	mrand "math/rand"
+	"testing"
+)
+
+func TestEncrypt(t *testing.T) {
+	dataSizes := []int{8, 13, 16, 32, 64, 1024, 1048576, 4194304, (mrand.Int() % 26214400) + 1}
+
+	for _, dataSize := range dataSizes {
+		key := make([]byte, 32)
+		_, err := rand.Read(key)
+		if err != nil {
+			t.Error("Failed to get random data from crypto/rand")
+		}
+		iv := make([]byte, 32)
+		_, err = rand.Read(iv)
+		if err != nil {
+			t.Error("Failed to get random data from crypto/rand")
+		}
+		data := make([]byte, dataSize)
+		_, err = rand.Read(data)
+		if err != nil {
+			t.Error("Failed to get random data from crypto/rand")
+		}
+
+		encrypted, err := Encrypt(key, iv, data)
+		if err != nil {
+			t.Error("Failed Encrypt with error: " + err.Error())
+		}
+
+		if bytes.Equal(encrypted, data) {
+			t.Error("Failed Encrypt: Encrypted data was the same as input data")
+		}
+
+		decrypted, err := Decrypt(key, iv, encrypted)
+		if err != nil {
+			t.Error("Failed Decrypt with error: " + err.Error())
+		}
+
+		cryptLen := len(decrypted)
+		for i := 0; i < cryptLen; i++ {
+			if i >= dataSize {
+				if decrypted[i] != 0 {
+					t.Error("Failed encryption/decryption: invalid padding")
+				}
+			} else if decrypted[i] != data[i] {
+				t.Error("Failed encryption/decryption: invalid data")
+			}
+		}
+	}
+
+	key := make([]byte, 31)
+	iv := make([]byte, 32)
+	data := make([]byte, 32)
+
+	_, err := Encrypt(key, iv, data)
+	if err == nil {
+		t.Error("Failed to receive error for invalid key size")
+	}
+
+	key = make([]byte, 32)
+	iv = make([]byte, 31)
+	_, err = Encrypt(key, iv, data)
+	if err == nil {
+		t.Error("Failed to receive error for invalid iv size")
+	}
+
+	key = make([]byte, 32)
+	iv = make([]byte, 32)
+	_, err = Encrypt(key, iv, []byte{})
+	if err == nil {
+		t.Error("Failed to receive error for 0 byte data size")
+	}
+}
+
+func TestDecrypt(t *testing.T) {
+	dataSizes := []int{8, 13, 16, 32, 64, 1024, 1048576, 4194304, (mrand.Int() % 26214400) + 1}
+
+	for _, dataSize := range dataSizes {
+		key := make([]byte, 32)
+		_, err := rand.Read(key)
+		if err != nil {
+			t.Error("Failed to get random data from crypto/rand")
+		}
+		iv := make([]byte, 32)
+		_, err = rand.Read(iv)
+		if err != nil {
+			t.Error("Failed to get random data from crypto/rand")
+		}
+		data := make([]byte, dataSize)
+		_, err = rand.Read(data)
+		if err != nil {
+			t.Error("Failed to get random data from crypto/rand")
+		}
+
+		encrypted, err := Encrypt(key, iv, data)
+		if err != nil {
+			t.Error("Failed Encrypt with error: " + err.Error())
+		}
+
+		if bytes.Equal(encrypted, data) {
+			t.Error("Failed Encrypt: Encrypted data was the same as input data")
+		}
+
+		decrypted, err := Decrypt(key, iv, encrypted)
+		if err != nil {
+			t.Error("Failed Decrypt with error: " + err.Error())
+		}
+
+		cryptLen := len(decrypted)
+		for i := 0; i < cryptLen; i++ {
+			if i >= dataSize {
+				if decrypted[i] != 0 {
+					t.Error("Failed encryption/decryption: invalid padding")
+				}
+			} else if decrypted[i] != data[i] {
+				t.Error("Failed encryption/decryption: invalid data")
+			}
+		}
+	}
+
+	key := make([]byte, 31)
+	iv := make([]byte, 32)
+	data := make([]byte, 32)
+
+	_, err := Decrypt(key, iv, data)
+	if err == nil {
+		t.Error("Failed to receive error for invalid key size")
+	}
+
+	key = make([]byte, 32)
+	iv = make([]byte, 31)
+	_, err = Decrypt(key, iv, data)
+	if err == nil {
+		t.Error("Failed to receive error for invalid iv size")
+	}
+
+	key = make([]byte, 32)
+	iv = make([]byte, 32)
+	data = make([]byte, 31)
+	if err == nil {
+		t.Error("Failed to receive error for invalid data size")
+	}
+
+	data = make([]byte, 0)
+	if err == nil {
+		t.Error("Failed to receive error for 0 byte data size")
+	}
+}