Paolo Ardoino - ideas, programming, web and more…

/* DES
 * If mode = DES_ENCRYPT encrypts *filein file with DES algorithm
 * If mode = DES_DECRYPT decrypts *filein file with DES algorithm
 * output is written in *fileout file
 * Returns 1 if the function runs successfully
 * Works on 8 bytes blocks
 *
 */
void des_encrypt_decrypt(int mode, char *filein, char *fileout)
{
        FILE *fpin,*fpout;
        char buf[MAXPASSLEN];
        des_cblock key,inmsg,outmsg; /* key, plaintext, ciphertext must be 8 byte blocks */
        des_key_schedule sched;
 
        if (strcmp(filein,fileout) == 0) {
                fprintf(stderr,"Error: input and output files must not be the same file.\n");
                exit(EXIT_FAILURE);
        }
        /* des_read_pw_string reads password from stdin and stores it in buf */
        /* this function automatically asks to re-enter password and checks it */
        memset(buf,'\0',MAXPASSLEN);
        if (mode == DES_ENCRYPT) {
                printf("Encrypting file '%s' with des cipher.\n",filein);
                if (des_read_pw_string(buf,MAXPASSLEN - 1,"Enter the password:\n",1) != 0) {
                        fprintf(stderr,"Error: failed to read password.\n");
                        exit(EXIT_FAILURE);
                }
        } else {
                printf("Decrypting file '%s' with des cipher.\n",filein);
                if (des_read_pw_string(buf,MAXPASSLEN - 1,"Enter the password:\n",0) != 0) {
                        fprintf(stderr,"Error: failed to read password.\n");
                        exit(EXIT_FAILURE);
                }
        }
        /* des_string to key convers the password to a key */
        des_string_to_key(buf,&key);
        /* des_set_key_checked checks that a key passed in of odd parity and set up the key schedule */
        des_set_key_checked(&key,sched);
        fpin = fopen(filein,"r");
        if ((fpout = fopen(fileout,"w")) == NULL) {
                fprintf(stderr,"Error: failed to open output file.\n");
                exit(EXIT_FAILURE);
        }
        /* reads 8 bytes at a time(block=8bytes),encrypts/decrypts each block with ecb */
        while (fread(inmsg,1,8,fpin)) {
                memset(outmsg,'\0',8);
                des_ecb_encrypt(&inmsg,&outmsg,sched,mode);
                fwrite(outmsg,1,8,fpout);
                memset(inmsg,'\0',8);
        }
        fclose(fpin);
        fclose(fpout);
        printf("Done.\n");
        return;
}
 
/* Blowfish
 * If mode = BF_ENCRYPT encrypts *filein file with Blowfish algorithm
 * If mode = BF_DECRYPT decrypts *filein file with Blowfish algorithm
 * output is written in *fileout file
 * Returns 1 if the function runs successfully
 * Works on 8 bytes blocks
 *
 */
void bf_encrypt_decrypt(int mode, char *filein, char *fileout)
{
        FILE *fpin,*fpout;
        char buf[MAXPASSLEN];
        unsigned char inmsg[8],outmsg[8]; /* blowfish operates on 8 byte blocks */
        BF_KEY key;
 
        if (strcmp(filein,fileout) == 0) {
                fprintf(stderr,"Error: input and output files must not be the same file.\n");
                exit(EXIT_FAILURE);
        }
        /* reads password from stdin using the same function used for des passwords */
        memset(buf,'\0',MAXPASSLEN);
        if (mode == BF_ENCRYPT) {
                printf("Encrypting file '%s' with BlowFish cipher.\n",filein);
                if (des_read_pw_string(buf,MAXPASSLEN - 1,"Enter the password:\n",1) != 0) {
                        fprintf(stderr,"Error: failed to read password.\n");
                        exit(EXIT_FAILURE);
                }
        } else {
                printf("Decrypting file '%s' with BlowFish cipher.\n",filein);
                if (des_read_pw_string(buf,MAXPASSLEN - 1,"Enter the password:\n",0) != 0) {
                        fprintf(stderr,"Error: failed to read password.\n");
                        exit(EXIT_FAILURE);
                }
        }
        /* set up the key using password stored in buf from des_read_pw_string */
        BF_set_key(&key,strlen(buf),buf);
        fpin = fopen(filein,"r");
        if ((fpout = fopen(fileout,"w")) == NULL) {
                fprintf(stderr,"Error: failed to open output file.\n");
                exit(EXIT_FAILURE);
        }
        /* reads 8 bytes at a time(block=8bytes),encrypts/decrypts each block with ecb */
        while (fread(inmsg,1,8,fpin)) {
                memset(outmsg,'\0',8);
                BF_ecb_encrypt(inmsg,outmsg,&key,mode);
                fwrite(outmsg,1,8,fpout);
                memset(inmsg,'\0',8);
        }
        fclose(fpin);
        fclose(fpout);
        printf("Done.\n");
        return;
}