dbms_crypto_toolkit error

Env: Oracle 8.0.5.1 on solaris

I'm trying to use dbms_crypto_toolkit package to encrypt strings. It gives this error:

declare
*
ERROR at line 1:

ORA-06550: line 10, column 11:
PLS-00307: too many declarations of 'ENCRYPT' match this call
ORA-06550: line 10, column 3:

My code is:

declare
  ps dbms_crypto_toolkit.Persona := null;   i number;
  str1 varchar2(1000);
begin
  dbms_crypto_toolkit.Initialize;
  dbms_crypto_toolkit.CreatePersona(dbms_crypto_toolkit.MD5,     null, 'aaa', 'aaa', 'aaa', ps);
  str1 := 'aaa';
  str1 := dbms_crypto_toolkit.Encrypt(ps, str1);   dbms_crypto_toolkit.Terminate;

end;
/ Received on Wed Sep 08 1999 - 00:00:00 CEST