idcrypt.c File Reference

Encryption/decryption of subject names and other identification information in string form. More...

#include "libtpcmisc.h"

Go to the source code of this file.

Functions
const char *	libpet_idcrypt_version (void)
int	id_crypt (const char *string, const char *key, char *out, int decrypt)

Detailed Description

Encryption/decryption of subject names and other identification information in string form.

Author

Calle Laakkonen

Note

Method is simple and not safe for data transfer over internet, but can be used to hide identification in blinded studies.

Definition in file idcrypt.c.

Function Documentation

id_crypt()

int id_crypt	(	const char *	string,
		const char *	key,
		char *	out,
		int	decrypt )

Scramble characters in ASCII range 32-126 using the Vigenere Cipher. Other characters are discarded.

Returns

Returns 0 if successful

Parameters

string	Original string to be encrypted/decrypted
key	Keyword string
out	Encrypted/decrypted string
decrypt	Set to 1 when decrypting, or to 0 when encrypting

Definition at line 23 of file idcrypt.c.

  {
    char *keystr;
    unsigned int len, r;
 
    len=strlen(string);
    if(len==0) return 0;
 
    keystr = malloc(len);
    if(!keystr) return 1;
 
    if(len>strlen(key)) {
        for(r=0;r<len;r++) {
            keystr[r]=key[r%strlen(key)]-32;
            if(keystr[r]>94) keystr[r]=94;
        }
    } else {
        for(r=0;r<len;r++) {
            keystr[r]=key[r]-32;
            if(keystr[r]>94) keystr[r]=94;
        }
    }
 
    for(r=0;r<len;r++) {
        int c=(unsigned char)string[r]-32;
        if(c>94) c=94;
        if(decrypt) {
            c=c-keystr[r];
            if(c<0) c=(95-(-c)%95);
        } else {
            c=(c+keystr[r])%95;
        }
        out[r]=c+32;
    }
    out[r]=0;
    free(keystr);
    return 0;
}

Referenced by id_crypt().

libpet_idcrypt_version()

const char * libpet_idcrypt_version

(

void

)

Return idcrypt module version info

Definition at line 15 of file idcrypt.c.

                                         {
    return "2004-12-14";
}

Referenced by libpet_idcrypt_version().