Java CryptoAPI 3DES Key Compatibility

[Michael Bebenita]

Hi,

A Java application is encrypting a block of text using 3DES ECB mode
and PKCS5 padding. I need to decrypt this text using C#. I've
extracted the 192 bit key using the getEncoded() method of the
SecretKey Java class. However when I use this key in .NET i cannot
decrypt the cipher text.

I am pretty sure that all my settings are correct, as far as setting
the ECB mode, PKCS5 padding and converting the cipher text to byte
arrays. I think it's the key that is giving me problems. Is there
anything that I must do to the exported java key before I use it in
..NET ?

Thanks
Michael Bebenita

[Gerard Krupa]

Re: Java CryptoAPI 3DES Key Compatibility

"Michael Bebenita" <thepuppet@sbcg lobal.net> wrote in message
news:826f20ab.0 309032241.4c7d1 d7b@posting.goo gle.com...[color=blue]
>
> A Java application is encrypting a block of text using 3DES ECB mode
> and PKCS5 padding. I need to decrypt this text using C#. I've
> extracted the 192 bit key using the getEncoded() method of the
> SecretKey Java class. However when I use this key in .NET i cannot
> decrypt the cipher text.
>
> I am pretty sure that all my settings are correct, as far as setting
> the ECB mode, PKCS5 padding and converting the cipher text to byte
> arrays. I think it's the key that is giving me problems. Is there
> anything that I must do to the exported java key before I use it in
> .NET ?[/color]

AFAIK, Java provides you with a 192-bit parity-adjusted key and .NET
requires a 168-bit non-parity-adjusted key. I don't think there is any
function in Java or .NET to remove the parity but it's simple enough to
implement (just a case of removing the LSB of each byte in the key).

You also need to ensure that your IV is shared between the two applications.

HTH

--
Gerard John Krupa BSc AMBCS
Purveyor of network management software

http://www.bogbrushzone.co.uk/

[Michael Bebenita]

Re: Java CryptoAPI 3DES Key Compatibility

"Gerard Krupa" <gerard@spamfre ebogbrush-zone.co.uk> wrote in message news:<dhG6b.91$ ca7.31@newsfep1-gui.server.ntli .net>...[color=blue]
> "Michael Bebenita" <thepuppet@sbcg lobal.net> wrote in message
> news:826f20ab.0 309032241.4c7d1 d7b@posting.goo gle.com...[color=green]
> >
> > A Java application is encrypting a block of text using 3DES ECB mode
> > and PKCS5 padding. I need to decrypt this text using C#. I've
> > extracted the 192 bit key using the getEncoded() method of the
> > SecretKey Java class. However when I use this key in .NET i cannot
> > decrypt the cipher text.
> >
> > I am pretty sure that all my settings are correct, as far as setting
> > the ECB mode, PKCS5 padding and converting the cipher text to byte
> > arrays. I think it's the key that is giving me problems. Is there
> > anything that I must do to the exported java key before I use it in
> > .NET ?[/color]
>
> AFAIK, Java provides you with a 192-bit parity-adjusted key and .NET
> requires a 168-bit non-parity-adjusted key. I don't think there is any
> function in Java or .NET to remove the parity but it's simple enough to
> implement (just a case of removing the LSB of each byte in the key).
>
> You also need to ensure that your IV is shared between the two applications.
>
> HTH[/color]

Thanks for the reply,

I tired extracting the 168 bit key by removing the parity bit. However
now I get a "Specified key is not a valid size for this algorithm."
exception when i try to use the key. I remember reading somewhere that
..NET / Crypto API igonore the parity bit anyways.

Michael

[Michael Bebenita]

Re: Java CryptoAPI 3DES Key Compatibility

thepuppet@sbcgl obal.net (Michael Bebenita) wrote in message news:<826f20ab. 0309071711.5e44 b2a4@posting.go ogle.com>...[color=blue]
> "Gerard Krupa" <gerard@spamfre ebogbrush-zone.co.uk> wrote in message news:<dhG6b.91$ ca7.31@newsfep1-gui.server.ntli .net>...[color=green]
> > "Michael Bebenita" <thepuppet@sbcg lobal.net> wrote in message
> > news:826f20ab.0 309032241.4c7d1 d7b@posting.goo gle.com...[color=darkred]
> > >
> > > A Java application is encrypting a block of text using 3DES ECB mode
> > > and PKCS5 padding. I need to decrypt this text using C#. I've
> > > extracted the 192 bit key using the getEncoded() method of the
> > > SecretKey Java class. However when I use this key in .NET i cannot
> > > decrypt the cipher text.
> > >
> > > I am pretty sure that all my settings are correct, as far as setting
> > > the ECB mode, PKCS5 padding and converting the cipher text to byte
> > > arrays. I think it's the key that is giving me problems. Is there
> > > anything that I must do to the exported java key before I use it in
> > > .NET ?[/color]
> >
> > AFAIK, Java provides you with a 192-bit parity-adjusted key and .NET
> > requires a 168-bit non-parity-adjusted key. I don't think there is any
> > function in Java or .NET to remove the parity but it's simple enough to
> > implement (just a case of removing the LSB of each byte in the key).
> >
> > You also need to ensure that your IV is shared between the two applications.
> >
> > HTH[/color]
>
> Thanks for the reply,
>
> I tired extracting the 168 bit key by removing the parity bit. However
> now I get a "Specified key is not a valid size for this algorithm."
> exception when i try to use the key. I remember reading somewhere that
> .NET / Crypto API igonore the parity bit anyways.
>
> Michael[/color]

Forget all that, there was no compatibility problem. The error had to
do with something unrelated.