blog/static/files/pb071/bonuses/05-06/bmp.h

99 lines
4 KiB
C
Raw Normal View History

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