I am trying to write an MD5 function in PL/SQL for oracle. I am however getting an error message

PLS-00307: too many declarations of 'MD5' match this call

Any suggestions to what is wrong?

Thanks

function MD5(str varchar2)

RETURN VARCHAR2 IS

md_str VARCHAR2(16);


BEGIN
md_str := dbms_obfuscation_toolkit.md5(str);

return md_str;

END;