Re: Triple DES Perl to Java

From:

"Oliver Wong" <owong@castortech.com>

Newsgroups:

comp.lang.java.programmer,comp.lang.java.security

Date:

Fri, 08 Sep 2006 21:26:31 GMT

Message-ID:

<belMg.272$cz3.219@edtnps82>

"Alex" <root@example.com> wrote in message
news:44ed980b$0$97229$892e7fe2@authen.yellow.readfreenews.net...

Mr. Skeptic wrote:

Looks pretty good. One likely problem is that the perl module processes
the key slightly differently. I'm not really a perl expert, but it
looks like perl treats the $passphrase argument as a 48-byte hex-ASCII
encoded key.

As an added twist, the perl pack function will just use
the last four bits of the ASCII code for non-hex characters, i.e. if
the letter 'k' is put in $passphrase it will be treated as if it was
the hex character 'b'.

I cant really follow this. How is a non-hex character transformed into a
hex one? Or more specific, how is k transformed to b?

b is ascii 98 is binary 0110 0010
k is ascii 107 is binary 0110 1011

The first nibble is identical, but the second isnt. How would this work?

    The hexadecimal value 'b' is equal to the decimal value '11', which is
equal to the binary value '1011' which is the lower half of the ASCII
representation of the character 'k'.

    So char 'k' -> 0xb.

    - Oliver