DBMS_CRYPTO - Key length is limited to 8 characters

Question

Hi, I have created a package to encrypt/decrypt the data.. But unfortunately it is considering only the first 8 characters to encrypt the data. Can anyone tell me why this behaviour and how can I fix this...
Also I would like to know is there a better way to do this...
PLEASE NOTE: when I change the key from v to w or when I change from 0 to 1 it’s the same hash value...
It takes the last two character pattern... for example, 2&3, 4 & 5, 6 & 7, 8 & 9, a & b, c & d etc., will get the same key... Also it is only using the first 8 characters to do the encryption.
SQL> select p_encrypt.encrypt_ssn('SUNILV,Kak93_dixj', 'v1qr3b9g') from dual;
P_ENCRYPT.ENCRYPT_SSN('SUNILV,KAK93_DIXJ','V1QR3B9G')
D4673C6035A01195D3BBB10F6AFA0BF44C673C79FE0044BF
SQL> select p_encrypt.encrypt_ssn('SUNILV,Kak93_dixj', 'w1qr3b9g') from dual;
P_ENCRYPT.ENCRYPT_SSN('SUNILV,KAK93_DIXJ','W1QR3B9G')
D4673C6035A01195D3BBB10F6AFA0BF44C673C79FE0044BF
SQL> select p_encrypt.encrypt_ssn('SUNILV,Kak93_dixj', 'w0qr3b9g') from dual;
P_ENCRYPT.ENCRYPT_SSN('SUNILV,KAK93_DIXJ','W0QR3B9G')
D4673C6035A01195D3BBB10F6AFA0BF44C673C79FE0044BF
SQL> select p_encrypt.encrypt_ssn('SUNILV,Kak93_dixj', 'w0qr3b9ga') from dual;
P_ENCRYPT.ENCRYPT_SSN('SUNILV,KAK93_DIXJ','W0QR3B9GA')
D4673C6035A01195D3BBB10F6AFA0BF44C673C79FE0044BF
SQL> select p_encrypt.encrypt_ssn('SUNILV,Kak93_dixj', 'w0qr3b9gab') from dual;
P_ENCRYPT.ENCRYPT_SSN('SUNILV,KAK93_DIXJ','W0QR3B9GAB')
D4673C6035A01195D3BBB10F6AFA0BF44C673C79FE0044BF
SQL> select p_encrypt.encrypt_ssn('SUNILV,Kak93_dixj', 'w0qr3b9gcb') from dual;
P_ENCRYPT.ENCRYPT_SSN('SUNILV,KAK93_DIXJ','W0QR3B9GCB')
D4673C6035A01195D3BBB10F6AFA0BF44C673C79FE0044BF
SQL> select p_encrypt.encrypt_ssn('SUNILV,Kak93_dixj', 'w0qr3b9gcbddkkdkdkkakaaa') from dual;
P_ENCRYPT.ENCRYPT_SSN('SUNILV,KAK93_DIXJ','W0QR3B9GCBDDKKDKDKKAKAAA')
D4673C6035A01195D3BBB10F6AFA0BF44C673C79FE0044BF
SQL>
CREATE OR REPLACE PACKAGE SECURITY.p_encrypt is
FUNCTION encrypt_ssn ( p_ssn IN VARCHAR2
, p_key IN VARCHAR2 ) RETURN RAW;
FUNCTION decrypt_ssn ( p_ssn IN RAW
, p_key IN VARCHAR2 ) RETURN VARCHAR2;
END p_encrypt;
CREATE OR REPLACE PACKAGE BODY SECURITY.p_encrypt AS
FUNCTION encrypt_ssn( p_ssn IN VARCHAR2
, p_key IN VARCHAR2 ) RETURN RAW
IS
l_ssn RAW(30) := UTL_I18N.STRING_TO_RAW(p_ssn, 'AL32UTF8' );
l_encrypted RAW(30);
BEGIN
NULL;
l_encrypted := dbms_crypto.encrypt
( src => l_ssn,
typ => DBMS_CRYPTO.DES_CBC_PKCS5 ,
key => UTL_I18N.STRING_TO_RAW( p_key, 'AL32UTF8' ) );
RETURN l_encrypted;
END encrypt_ssn;
FUNCTION decrypt_ssn( p_ssn IN RAW
, p_key IN VARCHAR2 ) RETURN VARCHAR2
IS
l_decrypted RAW(30);
BEGIN
l_decrypted := dbms_crypto.decrypt
( src => p_ssn,
typ => DBMS_CRYPTO.DES_CBC_PKCS5,
key => UTL_I18N.STRING_TO_RAW( p_key, 'AL32UTF8' ) );
RETURN UTL_I18N.RAW_TO_CHAR( l_decrypted, 'AL32UTF8' );
END decrypt_ssn;
END p_encrypt;
/

Answer 1

Try to use 3DES or AES algorithms. DES algorithm uses 56 bit key.
And now about keys: in this case dbms_crypto substracts first 8 bytes of the key value and then uses last 7 bytes (56 bits).