[Zefir]

Tiny Encryption Algorithm (TEA).
Simple and fast symmetric-key algorithm cipher.

.: Description

Tiny Encryption Algorithm (TEA) is a block cipher notable for its simplicity of description and implementation, typically a few lines of code. It was designed by David Wheeler and Roger Needham of the Cambridge Computer Laboratory; it was first presented at the Fast Software Encryption workshop in Leuven in 1994, and first published in the proceedings of that workshop.

The cipher is not subject to any patents.

.: Links
Page of project
Official site
Wikipedia page

.: TEA

TEA operates on 64-bit blocks and uses a 128-bit key. Password must be declaration as pass[4], but string as array with 2 cell.

.: XTEA

Like TEA, XTEA is a 64-bit block Feistel network with a 128-bit key and a suggested 64 rounds. Several differences from TEA are apparent, including a somewhat more complex key-schedule and a rearrangement of the shifts, XORs, and additions.


.: Stocks
Length of the string must be even

stock tea_crypt_str(str[], key[4]) :
— crypt string with key
stock tea_decrypt_str(str[], key[4]) :
— decrypt string with key
stock tea_crypt(str[2], key[4]) :
— crypt 2 cell array with key
stock tea_decrypt(str[2], key[4]) :
— decrypt 2 cell array with key
stock xtea_crypt_str(str[], key[4]) :
— crypt string with key
stock xtea_decrypt_str(str[], key[4]) :
— decrypt string with key
stock xtea_crypt(str[2], key[4]) :
— crypt 2 cell array with key
stock xtea_decrypt(str[2], key[4]) :
— decrypt 2 cell array with key


.: Examples
Key creation

Key is composed from ordinary string of 16 characters length to packed array of 4 cell 4 bytes each.

PHP Code:

get_password_key() {
    new password[17], key[4];
    // get password string
    get_cvar_string("password", password, charsmax(password));
    // pack key
    new i = 0;
    while (password[i] != EOS) 
        key{i} = password[i++]

    return key
} 


Prepare string to crypt

If length is not even last odd character is not encrypted

PHP Code:

crypt_string(str[]) {
    new key[4] = get_password_key();
    new ch = EOS, len = strlen(str);

    // save last odd char
    if (len & 1)
        ch = str[--len];

    // replace last char to the end of the string
    str[len] = EOS;
    xtea_crypt_string(str, key);
    // restore last char
    str[len] = ch;
}

decrypt_string(str[]) {
    new key[4] = get_password_key();
    new ch = EOS, len = strlen(str);
    
    // save last odd char
    if (len & 1)
        ch = str[--len];

    // replace last char to the end of the string
    str[len] = EOS;
    xtea_decrypt_string(str, key);
    // restore last char
    str[len] = ch;
}