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Asked: 2026-05-26T19:04:28+00:00

I’m trying to encrypt a string with rijndael (keysize 256 bit, blocksize 256 bit,

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I’m trying to encrypt a string with rijndael (keysize 256 bit, blocksize 256 bit, CFB mode)
currently i’m doing something like this:

BufferedBlockCipher c = new BufferedBlockCipher(new CFBBlockCipher(new RijndaelEngine(256), 256));
    c.init(false, new ParametersWithIV(new KeyParameter(keybytes), iv));

I can encrypt and decrypt my own stuff just fine. Unfortunately the string i have to decrypt comes from mcrypt in php.

I cant decrypt this string and i guess the failure is on my side. could anybody give me an example how to configure a cipher with the required parameters?

EDIT:

following some advice here and in the php documentation comments. i changed my cypher to:

PaddedBufferedBlockCipher c = new PaddedBufferedBlockCipher(new CFBBlockCipher(new RijndaelEngine(256)), new ZeroBytePadding());

still the encryptions are not compatible.

EDIT 2

got it working in CBC mode. I guess the problem is somewhere in iv.

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1 Answer

  1. Editorial Team
    PaddedBufferedBlockCipher c = new PaddedBufferedBlockCipher(new CFBBlockCipher(new RijndaelEngine(256), 8), new ZeroBytePadding());
c.init(false, new ParametersWithIV(new KeyParameter(keybytes), iv));

    this did the trick. All examples and tutorials say that the second param of the CFBBlockCipher object is the blocksize of the chiffre, which would work, but mcrypt uses a blocksize of 8 bit for CFB.

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