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99 lines
4 KiB
C
99 lines
4 KiB
C
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#ifndef _BMP_H
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#define _BMP_H
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/**
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* Return reversed string.
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*
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* Function returns a pointer to the reversed string, which has been created
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* from the input parameter. If the input string is NULL or memory could not be
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* allocated, function returns NULL.
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*
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* @param text input string
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* @return reversed representation of input string, or NULL, if the string could
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* not be created.
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*/
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char *reverse(const char *text);
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/**
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* Function for encrypting the given plaintext by applying the Vigenère cipher.
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*
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* @param key Pointer to a string representing the key which will be used
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* for encrypting the plaintext. The key is represented by a single
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* case-insensitive word consisting of only alphabetical characters.
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* @param text Pointer to a string representing the plaintext to be
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* encrypted.
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* @return the address of a copy of the ciphertext encrypted by the Vigenère
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* cipher, or NULL if the encryption was not successful.
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*/
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char *vigenere_encrypt(const char *key, const char *text);
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/**
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* Function for decrypting the given ciphertext by applying the Vigenère cipher.
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*
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* @param key Pointer to a string representing the key which has been used
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* for encrypting the ciphertext. The key is represented by a single
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* case-insensitive word consisting of only alphabetical characters.
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* @param text Pointer to a string representing the ciphertext to be
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* decrypted.
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* @return the address of a copy of the plaintext decrypted by the Vigenère
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* cipher, or NULL if the decryption was not successful.
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*/
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char *vigenere_decrypt(const char *key, const char *text);
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/**
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* Function for bitwise encryption according to the following process:
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* The character about to be encrypted is divided in half (4 bits + 4 bits).
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* Subsequently, the bits in the left half are divided into two pairs and the
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* values inside each pair are swapped. The four bits created by this way are
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* then used in a bitwise XOR operation with the remaining 4 bits.
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*
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* @param text String representing the plaintext to be encrypted.
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* @return a pointer to a newly created string containing the ciphertext
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* produced by encrypting the plaintext, or NULL if the encryption was not
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* successful.
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*/
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unsigned char *bit_encrypt(const char *text);
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/**
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* Function for bitwise decryption - it is the inverse of the bitwise encryption
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* function.
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*
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* @param text String representing the ciphertext to be decrypted.
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* @return a pointer to a newly created string containing the plaintext produced
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* by decrypting the ciphertext, or NULL if the decryption was not successful.
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*/
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char *bit_decrypt(const unsigned char *text);
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/**
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* Function for encrypting the given plaintext by applying the BMP cipher.
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* The process of encrypting by BMP:
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* <ol>
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* <li> the provided input string is encrypted by function reverse()
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* <li> the acquired string is encrypted by function vigenere_encrypt()
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* <li> function bit_encrypt() is applied on the resulting string
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* </ol>
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*
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* @param key Pointer to a string representing the key which will be used
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* for encrypting the plaintext. The key is represented by a single
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* case-insensitive word consisting of only alphabetical characters.
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* @param text String representing the plaintext to be encrypted.
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* @return the address of a copy of the ciphertext encrypted by the BMP cipher,
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* or NULL if the encryption was not successful.
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*/
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unsigned char *bmp_encrypt(const char *key, const char *text);
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/**
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* Function for decrypting the given ciphertext by applying the BMP cipher.
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* The process of decrypting by BMP is the opposite of BMP encryption.
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*
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* @param key Pointer to a string representing the key which has been used
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* for encrypting the ciphertext. The key is represented by a single
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* case-insensitive word consisting of only alphabetical characters.
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* @param text String representing the ciphertext to be decrypted.
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* @return the address of a copy of the plaintext decrypted by the BMP cipher,
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* or NULL if the decryption was not successful.
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*/
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char *bmp_decrypt(const char *key, const unsigned char *text);
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#endif
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