Field encryption

Question

Does anyone know what I need to do to encrypt the values for a particular field in a table?, rather than using views/roles or fine-grained access control,
thanks.

Answer 1

I used the following functions to encode, respectively decode sonething.
Function n_code ( V$S in varchar2 ) RETURN varchar2
IS
phrase varchar2(10):='Your Key Phrase'; -- CONSTANT
s1 varchar2(1);
s2 varchar2(1);
x number;
y number;
V_Temp varchar2(10):='';
BEGIN
for count in 1..length(V$S) loop
s1:=substr(V$S,count,1);
s2:=substr(Phrase,count,1);
x:=ascii(s1);
y:=ascii(s2);
x:=mod(x+y,256);
s1:=chr(x);
V_Temp:=concat(V_Temp,s1);
--dbms_output.put_line(s1);
end loop;
-- dbms_output.put_line(retur);
RETURN V_Temp;
EXCEPTION WHEN OTHERS THEN RETURN NULL;
END;
Function d_code ( V$S in varchar2 ) RETURN varchar2
IS
phrase varchar2(10):='Your Key Phrase'; -- CONSTANT !!!
s1 varchar2(1);
s2 varchar2(1);
x number;
y number;
V_Temp varchar2(10):='';
BEGIN
for count in 1..length(V$S) loop
s1:=substr(V$S,count,1);
s2:=substr(phrase,count,1);
x:=ascii(s1);
y:=ascii(s2);
x:=x-y;
if x<0 then
x:=x+256;
end if;
s1:=chr(x);
V_Temp:=concat(V_Temp,s1);
--dbms_output.put_line(s1);
end loop;
If the string that is to be encoded is longer than the key phrase, you mai decompose it in groups of letters that have the length of your key phrase and encode/decode each group using these functions.
Moreover, to make things more complicated, hard to break even when using a computer program, you may have an aditional field that holds the date&time when the record was changed, value that you may use to mix-up your key phrase, something like the following:
-- v$d being the date
nmixer:=to_number(to_char(v$d, 'mi'))+to_number(to_char(v$d, 'ss'));
nmixer:=mod(nmixer, 16);
phrase:=substr(phrase, nmixer, mod(nmixer, 9))&#0124; &#0124;phrase;
This is what I used and provides a means to actually encode and decode whatever data you need.
All these functions are stored in the DB in a wrapped package, to be sure not even the DBA can break it.
Some other way to check, say for a password is to use dbms_utility.get_hash_value, and compare the result of hash_value for the value entered by the user to the hashed value stored in the DB.
You may choose whatever seems fit for your purpouse.
Regards,
BD.