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+/*
+ * Fast, portable, and easy-to-use Twofish implementation,
+ * Version 0.3.
+ * Copyright (c) 2002 by Niels Ferguson.
+ *
+ * See the twofish.c file for the details of the how and why of this code.
+ *
+ * The author hereby grants a perpetual license to everybody to
+ * use this code for any purpose as long as the copyright message is included
+ * in the source code of this or any derived work.
+ */
+
+
+/*
+ * PLATFORM FIXES
+ * ==============
+ *
+ * The following definitions have to be fixed for each particular platform
+ * you work on. If you have a multi-platform program, you no doubt have
+ * portable definitions that you can substitute here without changing
+ * the rest of the code.
+ *
+ * The defaults provided here should work on most PC compilers.
+ */
+
+#ifndef TWOFISH_H
+#define TWOFISH_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/**
+ * @file twofish.h
+ * @brief Function that provide basic Twofish crypto support
+ *
+ * @ingroup GNU_ZRTP
+ * @{
+ */
+
+/**
+ * A Twofish_Byte must be an unsigned 8-bit integer.
+ *
+ * It must also be the elementary data size of your C platform,
+ * i.e. sizeof( Twofish_Byte ) == 1.
+ */
+typedef unsigned char Twofish_Byte;
+
+/**
+ * A Twofish_UInt32 must be an unsigned integer of at least 32 bits.
+ *
+ * This type is used only internally in the implementation, so ideally it
+ * would not appear in the header file, but it is used inside the
+ * Twofish_key structure which means it has to be included here.
+ */
+typedef unsigned int Twofish_UInt32;
+
+
+/*
+ * END OF PLATFORM FIXES
+ * =====================
+ *
+ * You should not have to touch the rest of this file, but the code
+ * in twofish.c has a few things you need to fix too.
+ */
+
+/**
+ * Return codes
+ */
+#define SUCCESS 1
+#define ERR_UINT32 -2
+#define ERR_BYTE -3
+#define ERR_GET32 -4
+#define ERR_PUT32 -5
+#define ERR_ROLR -6
+#define ERR_BSWAP -7
+#define ERR_SELECTB -8
+#define ERR_TEST_ENC -9
+#define ERR_TEST_DEC -10
+#define ERR_SEQ_ENC -11
+#define ERR_SEQ_DEC -12
+#define ERR_ODD_KEY -13
+#define ERR_INIT -14
+#define ERR_KEY_LEN -15
+#define ERR_ILL_ARG -16
+
+
+/**
+ * Structure that contains a prepared Twofish key.
+ *
+ * A cipher key is used in two stages. In the first stage it is converted
+ * form the original form to an internal representation.
+ * This internal form is then used to encrypt and decrypt data.
+ * This structure contains the internal form. It is rather large: 4256 bytes
+ * on a platform with 32-bit unsigned values.
+ *
+ * Treat this as an opague structure, and don't try to manipulate the
+ * elements in it. I wish I could hide the inside of the structure,
+ * but C doesn't allow that.
+ */
+typedef
+ struct
+ {
+ Twofish_UInt32 s[4][256]; /* pre-computed S-boxes */
+ Twofish_UInt32 K[40]; /* Round key words */
+ }
+ Twofish_key;
+
+
+/**
+ * Initialise and test the Twofish implementation.
+ *
+ * This function MUST be called before any other function in the
+ * Twofish implementation is called.
+ * It only needs to be called once.
+ *
+ * Apart from initialising the implementation it performs a self test.
+ * If the Twofish_fatal function is not called, the code passed the test.
+ * (See the twofish.c file for details on the Twofish_fatal function.)
+ *
+ * @returns a negative number if an error happend, +1 otherwise
+ */
+extern int Twofish_initialise();
+
+
+/**
+ * Convert a cipher key to the internal form used for
+ * encryption and decryption.
+ *
+ * The cipher key is an array of bytes; the Twofish_Byte type is
+ * defined above to a type suitable on your platform.
+ *
+ * Any key must be converted to an internal form in the Twofisk_key structure
+ * before it can be used.
+ * The encryption and decryption functions only work with the internal form.
+ * The conversion to internal form need only be done once for each key value.
+ *
+ * Be sure to wipe all key storage, including the Twofish_key structure,
+ * once you are done with the key data.
+ * A simple memset( TwofishKey, 0, sizeof( TwofishKey ) ) will do just fine.
+ *
+ * Unlike most implementations, this one allows any key size from 0 bytes
+ * to 32 bytes. According to the Twofish specifications,
+ * irregular key sizes are handled by padding the key with zeroes at the end
+ * until the key size is 16, 24, or 32 bytes, whichever
+ * comes first. Note that each key of irregular size is equivalent to exactly
+ * one key of 16, 24, or 32 bytes.
+ *
+ * WARNING: Short keys have low entropy, and result in low security.
+ * Anything less than 8 bytes is utterly insecure. For good security
+ * use at least 16 bytes. I prefer to use 32-byte keys to prevent
+ * any collision attacks on the key.
+ *
+ * The key length argument key_len must be in the proper range.
+ * If key_len is not in the range 0,...,32 this routine attempts to generate
+ * a fatal error (depending on the code environment),
+ * and at best (or worst) returns without having done anything.
+ *
+ * @param key Array of key bytes
+ * @param key_len Number of key bytes, must be in the range 0,1,...,32.
+ * @param xkey Pointer to an Twofish_key structure that will be filled
+ * with the internal form of the cipher key.
+ * @returns a negative number if an error happend, +1 otherwise
+ */
+extern int Twofish_prepare_key(
+ Twofish_Byte key[],
+ int key_len,
+ Twofish_key * xkey
+ );
+
+
+/**
+ * Encrypt a single block of data.
+ *
+ * This function encrypts a single block of 16 bytes of data.
+ * If you want to encrypt a larger or variable-length message,
+ * you will have to use a cipher mode, such as CBC or CTR.
+ * These are outside the scope of this implementation.
+ *
+ * The xkey structure is not modified by this routine, and can be
+ * used for further encryption and decryption operations.
+ *
+ * @param xkey pointer to Twofish_key, internal form of the key
+ * produces by Twofish_prepare_key()
+ * @param p Plaintext to be encrypted
+ * @param c Place to store the ciphertext
+ */
+extern void Twofish_encrypt(
+ Twofish_key * xkey,
+ Twofish_Byte p[16],
+ Twofish_Byte c[16]
+ );
+
+
+/**
+ * Decrypt a single block of data.
+ *
+ * This function decrypts a single block of 16 bytes of data.
+ * If you want to decrypt a larger or variable-length message,
+ * you will have to use a cipher mode, such as CBC or CTR.
+ * These are outside the scope of this implementation.
+ *
+ * The xkey structure is not modified by this routine, and can be
+ * used for further encryption and decryption operations.
+ *
+ * @param xkey pointer to Twofish_key, internal form of the key
+ * produces by Twofish_prepare_key()
+ * @param c Ciphertext to be decrypted
+ * @param p Place to store the plaintext
+ */
+extern void Twofish_decrypt(
+ Twofish_key * xkey,
+ Twofish_Byte c[16],
+ Twofish_Byte p[16]
+ );
+
+
+/**
+ * Encrypt data in CFB mode.
+ *
+ * This function encrypts data in CFB mode.
+ *
+ * The key structure is not modified by this routine, and can be
+ * used for further encryption and decryption operations.
+ *
+ * @param keyCtx pointer to Twofish_key, internal form of the key
+ * produced by Twofish_prepare_key()
+ * @param in Plaintext to be encrypted
+ * @param out Place to store the ciphertext
+ * @param len number of bytes to encrypt.
+ * @param ivec initialization vector for this CFB mode encryption.
+ * @param num pointer to integer that holds number of available crypto bytes.
+ */
+void Twofish_cfb128_encrypt(Twofish_key* keyCtx, Twofish_Byte* in,
+ Twofish_Byte* out, size_t len,
+ Twofish_Byte* ivec, int *num);
+
+/**
+ * Decrypt data in CFB mode.
+ *
+ * This function decrypts data in CFB.
+ *
+ * The key structure is not modified by this routine, and can be
+ * used for further encryption and decryption operations.
+ *
+ * @param keyCtx pointer to Twofish_key, internal form of the key
+ * produced by Twofish_prepare_key()
+ * @param in Ciphertext to be decrypted
+ * @param out Place to store the plaintext
+ * @param len number of bytes to decrypt.
+ * @param ivec initialization vector for this CFB mode encryption.
+ * @param num pointer to integer that holds number of available crypto bytes.
+ */
+void Twofish_cfb128_decrypt(Twofish_key* keyCtx, Twofish_Byte* in,
+ Twofish_Byte* out, size_t len,
+ Twofish_Byte* ivec, int *num);
+/**
+ * @}
+ */
+#ifdef __cplusplus
+}
+#endif
+
+#endif