Java CryptoAPI 3DES Key Compatibility

  • Thread starter Thread starter Michael Bebenita
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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
 
Michael Bebenita said:
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 ?
Click to expand...

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 Krupa said:
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
Click to expand...

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
 
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
Click to expand...

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