Move CBC, CFB, and OFB to the CryptoLegacy library

libraries/CryptoLegacy/src/CBC.cpp

@@ -0,0 +1,171 @@
+/*
+ * Copyright (C) 2015 Southern Storm Software, Pty Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "CBC.h"
+#include "Crypto.h"
+#include <string.h>
+
+/**
+ * \class CBCCommon CBC.h <CBC.h>
+ * \brief Concrete base class to assist with implementing CBC for
+ * 128-bit block ciphers.
+ *
+ * Reference: http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation
+ *
+ * \sa CBC
+ */
+
+/**
+ * \brief Constructs a new cipher in CBC mode.
+ *
+ * This constructor should be followed by a call to setBlockCipher().
+ */
+CBCCommon::CBCCommon()
+    : blockCipher(0)
+    , posn(16)
+{
+}
+
+/**
+ * \brief Destroys this cipher object after clearing sensitive information.
+ */
+CBCCommon::~CBCCommon()
+{
+    clean(iv);
+    clean(temp);
+}
+
+size_t CBCCommon::keySize() const
+{
+    return blockCipher->keySize();
+}
+
+size_t CBCCommon::ivSize() const
+{
+    return 16;
+}
+
+bool CBCCommon::setKey(const uint8_t *key, size_t len)
+{
+    // Verify the cipher's block size, just in case.
+    if (blockCipher->blockSize() != 16)
+        return false;
+
+    // Set the key on the underlying block cipher.
+    return blockCipher->setKey(key, len);
+}
+
+bool CBCCommon::setIV(const uint8_t *iv, size_t len)
+{
+    if (len != 16)
+        return false;
+    memcpy(this->iv, iv, 16);
+    posn = 16;
+    return true;
+}
+
+void CBCCommon::encrypt(uint8_t *output, const uint8_t *input, size_t len)
+{
+    uint8_t posn;
+    while (len >= 16) {
+        for (posn = 0; posn < 16; ++posn)
+            iv[posn] ^= *input++;
+        blockCipher->encryptBlock(iv, iv);
+        for (posn = 0; posn < 16; ++posn)
+            *output++ = iv[posn];
+        len -= 16;
+    }
+}
+
+void CBCCommon::decrypt(uint8_t *output, const uint8_t *input, size_t len)
+{
+    uint8_t posn;
+    while (len >= 16) {
+        blockCipher->decryptBlock(temp, input);
+        for (posn = 0; posn < 16; ++posn) {
+            uint8_t in = *input++;
+            *output++ = temp[posn] ^ iv[posn];
+            iv[posn] = in;
+        }
+        len -= 16;
+    }
+}
+
+void CBCCommon::clear()
+{
+    blockCipher->clear();
+    clean(iv);
+    clean(temp);
+    posn = 16;
+}
+
+/**
+ * \fn void CBCCommon::setBlockCipher(BlockCipher *cipher)
+ * \brief Sets the block cipher to use for this CBC object.
+ *
+ * \param cipher The block cipher to use to implement CBC mode,
+ * which must have a block size of 16 bytes (128 bits).
+ */
+
+/**
+ * \class CBC CBC.h <CBC.h>
+ * \brief Implementation of the Cipher Block Chaining (CBC) mode for
+ * 128-bit block ciphers.
+ *
+ * The template parameter T must be a concrete subclass of BlockCipher
+ * indicating the specific block cipher to use.  T must have a block size
+ * of 16 bytes (128 bits).
+ *
+ * For example, the following creates a CBC object using AES192 as the
+ * underlying cipher:
+ *
+ * \code
+ * CBC<AES192> cbc;
+ * cbc.setKey(key, 24);
+ * cbc.setIV(iv, 16);
+ * cbc.encrypt(output, input, len);
+ * \endcode
+ *
+ * Decryption is similar:
+ *
+ * \code
+ * CBC<AES192> cbc;
+ * cbc.setKey(key, 24);
+ * cbc.setIV(iv, 16);
+ * cbc.decrypt(output, input, len);
+ * \endcode
+ *
+ * The size of the ciphertext will always be the same as the size of
+ * the plaintext.  Also, the length of the plaintext/ciphertext must be a
+ * multiple of 16.  Extra bytes are ignored and not encrypted.  The caller
+ * is responsible for padding the underlying data to a multiple of 16
+ * using an appropriate padding scheme for the application.
+ *
+ * Reference: http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation
+ *
+ * \sa CTR, CFB, OFB
+ */
+
+/**
+ * \fn CBC::CBC()
+ * \brief Constructs a new CBC object for the block cipher T.
+ */

libraries/CryptoLegacy/src/CBC.h

@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2015 Southern Storm Software, Pty Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef CRYPTO_CBC_h
+#define CRYPTO_CBC_h
+
+#include "Cipher.h"
+#include "BlockCipher.h"
+
+class CBCCommon : public Cipher
+{
+public:
+    virtual ~CBCCommon();
+
+    size_t keySize() const;
+    size_t ivSize() const;
+
+    bool setKey(const uint8_t *key, size_t len);
+    bool setIV(const uint8_t *iv, size_t len);
+
+    void encrypt(uint8_t *output, const uint8_t *input, size_t len);
+    void decrypt(uint8_t *output, const uint8_t *input, size_t len);
+
+    void clear();
+
+protected:
+    CBCCommon();
+    void setBlockCipher(BlockCipher *cipher) { blockCipher = cipher; }
+
+private:
+    BlockCipher *blockCipher;
+    uint8_t iv[16];
+    uint8_t temp[16];
+    uint8_t posn;
+};
+
+template <typename T>
+class CBC : public CBCCommon
+{
+public:
+    CBC() { setBlockCipher(&cipher); }
+
+private:
+    T cipher;
+};
+
+#endif

libraries/CryptoLegacy/src/CFB.cpp

@@ -0,0 +1,195 @@
+/*
+ * Copyright (C) 2015 Southern Storm Software, Pty Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "CFB.h"
+#include "Crypto.h"
+#include <string.h>
+
+/**
+ * \class CFBCommon CFB.h <CFB.h>
+ * \brief Concrete base class to assist with implementing CFB for
+ * 128-bit block ciphers.
+ *
+ * Reference: http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation
+ *
+ * \sa CFB
+ */
+
+/**
+ * \brief Constructs a new cipher in CFB mode.
+ *
+ * This constructor should be followed by a call to setBlockCipher().
+ */
+CFBCommon::CFBCommon()
+    : blockCipher(0)
+    , posn(16)
+{
+}
+
+/**
+ * \brief Destroys this cipher object after clearing sensitive information.
+ */
+CFBCommon::~CFBCommon()
+{
+    clean(iv);
+}
+
+size_t CFBCommon::keySize() const
+{
+    return blockCipher->keySize();
+}
+
+size_t CFBCommon::ivSize() const
+{
+    return 16;
+}
+
+bool CFBCommon::setKey(const uint8_t *key, size_t len)
+{
+    // Verify the cipher's block size, just in case.
+    if (blockCipher->blockSize() != 16)
+        return false;
+
+    // Set the key on the underlying block cipher.
+    return blockCipher->setKey(key, len);
+}
+
+bool CFBCommon::setIV(const uint8_t *iv, size_t len)
+{
+    if (len != 16)
+        return false;
+    memcpy(this->iv, iv, 16);
+    posn = 16;
+    return true;
+}
+
+void CFBCommon::encrypt(uint8_t *output, const uint8_t *input, size_t len)
+{
+    uint8_t size;
+    while (len > 0) {
+        // If we have exhausted the current keystream block, then encrypt
+        // the IV/ciphertext to get another keystream block.
+        if (posn >= 16) {
+            blockCipher->encryptBlock(iv, iv);
+            posn = 0;
+        }
+
+        // XOR the plaintext with the encrypted IV to get the new ciphertext.
+        // We keep building up the ciphertext byte by byte in the IV buffer
+        // until we have a full block's worth, and then the IV is encrypted
+        // again by the code above.
+        size = 16 - posn;
+        if (size > len)
+            size = len;
+        len -= size;
+        while (size > 0) {
+            iv[posn] ^= *input++;
+            *output++ = iv[posn++];
+            --size;
+        }
+    }
+}
+
+void CFBCommon::decrypt(uint8_t *output, const uint8_t *input, size_t len)
+{
+    uint8_t size;
+    while (len > 0) {
+        // If we have exhausted the current keystream block, then encrypt
+        // the IV/ciphertext to get another keystream block.
+        if (posn >= 16) {
+            blockCipher->encryptBlock(iv, iv);
+            posn = 0;
+        }
+
+        // XOR the ciphertext with the encrypted IV to get the new plaintext.
+        // We keep building up the ciphertext byte by byte in the IV buffer
+        // until we have a full block's worth, and then the IV is encrypted
+        // again by the code above.
+        size = 16 - posn;
+        if (size > len)
+            size = len;
+        len -= size;
+        while (size > 0) {
+            uint8_t in = *input++;
+            *output++ = iv[posn] ^ in;
+            iv[posn++] = in;
+            --size;
+        }
+    }
+}
+
+void CFBCommon::clear()
+{
+    blockCipher->clear();
+    clean(iv);
+    posn = 16;
+}
+
+/**
+ * \fn void CFBCommon::setBlockCipher(BlockCipher *cipher)
+ * \brief Sets the block cipher to use for this CFB object.
+ *
+ * \param cipher The block cipher to use to implement CFB mode,
+ * which must have a block size of 16 bytes (128 bits).
+ */
+
+/**
+ * \class CFB CFB.h <CFB.h>
+ * \brief Implementation of the Cipher Feedback (CFB) mode for
+ * 128-bit block ciphers.
+ *
+ * The template parameter T must be a concrete subclass of BlockCipher
+ * indicating the specific block cipher to use.  T must have a block size
+ * of 16 bytes (128 bits).  The size of the CFB shift register is the same
+ * as the block size.
+ *
+ * For example, the following creates a CFB object using AES192 as the
+ * underlying cipher:
+ *
+ * \code
+ * CFB<AES192> cfb;
+ * cfb.setKey(key, 24);
+ * cfb.setIV(iv, 16);
+ * cfb.encrypt(output, input, len);
+ * \endcode
+ *
+ * Decryption is similar:
+ *
+ * \code
+ * CFB<AES192> cfb;
+ * cfb.setKey(key, 24);
+ * cfb.setIV(iv, 16);
+ * cfb.decrypt(output, input, len);
+ * \endcode
+ *
+ * The size of the ciphertext will always be the same as the size of
+ * the plaintext.
+ *
+ * Reference: http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation
+ *
+ * \sa CTR, OFB, CBC
+ */
+
+/**
+ * \fn CFB::CFB()
+ * \brief Constructs a new CFB object for the block cipher T.
+ */

libraries/CryptoLegacy/src/CFB.h

@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2015 Southern Storm Software, Pty Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef CRYPTO_CFB_h
+#define CRYPTO_CFB_h
+
+#include "Cipher.h"
+#include "BlockCipher.h"
+
+class CFBCommon : public Cipher
+{
+public:
+    virtual ~CFBCommon();
+
+    size_t keySize() const;
+    size_t ivSize() const;
+
+    bool setKey(const uint8_t *key, size_t len);
+    bool setIV(const uint8_t *iv, size_t len);
+
+    void encrypt(uint8_t *output, const uint8_t *input, size_t len);
+    void decrypt(uint8_t *output, const uint8_t *input, size_t len);
+
+    void clear();
+
+protected:
+    CFBCommon();
+    void setBlockCipher(BlockCipher *cipher) { blockCipher = cipher; }
+
+private:
+    BlockCipher *blockCipher;
+    uint8_t iv[16];
+    uint8_t posn;
+};
+
+template <typename T>
+class CFB : public CFBCommon
+{
+public:
+    CFB() { setBlockCipher(&cipher); }
+
+private:
+    T cipher;
+};
+
+#endif

libraries/CryptoLegacy/src/CryptoLegacy.h

@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2018 Southern Storm Software, Pty Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef CRYPTO_LEGACY_H
+#define CRYPTO_LEGACY_H
+
+// This header exists to make the Arudino IDE add the library to the
+// include and link paths when the sketch includes <CryptoLegacy.h>.
+
+#endif

libraries/CryptoLegacy/src/OFB.cpp

@@ -0,0 +1,160 @@
+/*
+ * Copyright (C) 2015 Southern Storm Software, Pty Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "OFB.h"
+#include "Crypto.h"
+#include <string.h>
+
+/**
+ * \class OFBCommon OFB.h <OFB.h>
+ * \brief Concrete base class to assist with implementing OFB for
+ * 128-bit block ciphers.
+ *
+ * Reference: http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation
+ *
+ * \sa OFB
+ */
+
+/**
+ * \brief Constructs a new cipher in OFB mode.
+ *
+ * This constructor should be followed by a call to setBlockCipher().
+ */
+OFBCommon::OFBCommon()
+    : blockCipher(0)
+    , posn(16)
+{
+}
+
+/**
+ * \brief Destroys this cipher object after clearing sensitive information.
+ */
+OFBCommon::~OFBCommon()
+{
+    clean(iv);
+}
+
+size_t OFBCommon::keySize() const
+{
+    return blockCipher->keySize();
+}
+
+size_t OFBCommon::ivSize() const
+{
+    return 16;
+}
+
+bool OFBCommon::setKey(const uint8_t *key, size_t len)
+{
+    // Verify the cipher's block size, just in case.
+    if (blockCipher->blockSize() != 16)
+        return false;
+
+    // Set the key on the underlying block cipher.
+    return blockCipher->setKey(key, len);
+}
+
+bool OFBCommon::setIV(const uint8_t *iv, size_t len)
+{
+    if (len != 16)
+        return false;
+    memcpy(this->iv, iv, 16);
+    posn = 16;
+    return true;
+}
+
+void OFBCommon::encrypt(uint8_t *output, const uint8_t *input, size_t len)
+{
+    uint8_t size;
+    while (len > 0) {
+        // If we have exhausted the current keystream block, then encrypt
+        // the IV/ciphertext to get another keystream block.
+        if (posn >= 16) {
+            blockCipher->encryptBlock(iv, iv);
+            posn = 0;
+        }
+
+        // XOR the plaintext with the encrypted IV to get the new ciphertext.
+        size = 16 - posn;
+        if (size > len)
+            size = len;
+        len -= size;
+        while (size > 0) {
+            *output++ = *input++ ^ iv[posn++];
+            --size;
+        }
+    }
+}
+
+void OFBCommon::decrypt(uint8_t *output, const uint8_t *input, size_t len)
+{
+    encrypt(output, input, len);
+}
+
+void OFBCommon::clear()
+{
+    blockCipher->clear();
+    clean(iv);
+    posn = 16;
+}
+
+/**
+ * \fn void OFBCommon::setBlockCipher(BlockCipher *cipher)
+ * \brief Sets the block cipher to use for this OFB object.
+ *
+ * \param cipher The block cipher to use to implement OFB mode,
+ * which must have a block size of 16 bytes (128 bits).
+ */
+
+/**
+ * \class OFB OFB.h <OFB.h>
+ * \brief Implementation of the Output Feedback (OFB) mode for
+ * 128-bit block ciphers.
+ *
+ * The template parameter T must be a concrete subclass of BlockCipher
+ * indicating the specific block cipher to use.  T must have a block size
+ * of 16 bytes (128 bits).
+ *
+ * For example, the following creates a OFB object using AES192 as the
+ * underlying cipher:
+ *
+ * \code
+ * OFB<AES192> ofb;
+ * ofb.setKey(key, 24);
+ * ofb.setIV(iv, 16);
+ * ofb.encrypt(output, input, len);
+ * \endcode
+ *
+ * Decryption is identical to encryption for OFB mode.
+ *
+ * The size of the ciphertext will always be the same as the size of
+ * the plaintext.
+ *
+ * Reference: http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation
+ *
+ * \sa CTR, CFB, CBC
+ */
+
+/**
+ * \fn OFB::OFB()
+ * \brief Constructs a new OFB object for the block cipher T.
+ */

libraries/CryptoLegacy/src/OFB.h

@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2015 Southern Storm Software, Pty Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef CRYPTO_OFB_h
+#define CRYPTO_OFB_h
+
+#include "Cipher.h"
+#include "BlockCipher.h"
+
+class OFBCommon : public Cipher
+{
+public:
+    virtual ~OFBCommon();
+
+    size_t keySize() const;
+    size_t ivSize() const;
+
+    bool setKey(const uint8_t *key, size_t len);
+    bool setIV(const uint8_t *iv, size_t len);
+
+    void encrypt(uint8_t *output, const uint8_t *input, size_t len);
+    void decrypt(uint8_t *output, const uint8_t *input, size_t len);
+
+    void clear();
+
+protected:
+    OFBCommon();
+    void setBlockCipher(BlockCipher *cipher) { blockCipher = cipher; }
+
+private:
+    BlockCipher *blockCipher;
+    uint8_t iv[16];
+    uint8_t posn;
+};
+
+template <typename T>
+class OFB : public OFBCommon
+{
+public:
+    OFB() { setBlockCipher(&cipher); }
+
+private:
+    T cipher;
+};
+
+#endif