Backslah in encrypt function.

Hi,
I have come on a problem regarding encryption. I am firing a simple
select statement:

select encrypt('\\','abcd','bf');

I want to use \ for encryption but I get the error:
"invalid input syntax for type bytea"

I tried using \\\\ to encrypt \ , but on decryption I get \\ instead of
\ (single backslash).

Could someone guide me regarding this,

Thanks in advance,
Nalin Bakshi.