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]

"Michael Bebenita" <th*******@sbcglobal.net> wrote in message
news:82**************************@posting.google.c om...

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 ?

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]

"Gerard Krupa" <ge****@spamfreebogbrush-zone.co.uk> wrote in message news:<dh*************@newsfep1-gui.server.ntli.net>...

"Michael Bebenita" <th*******@sbcglobal.net> wrote in message
news:82**************************@posting.google.c om...

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 ?

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

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]

th*******@sbcglobal.net (Michael Bebenita) wrote in message news:<82**************************@posting.google. com>...

"Gerard Krupa" <ge****@spamfreebogbrush-zone.co.uk> wrote in message news:<dh*************@newsfep1-gui.server.ntli.net>...

"Michael Bebenita" <th*******@sbcglobal.net> wrote in message
news:82**************************@posting.google.c om...

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 ?

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

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

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