AES BadPaddingException?

You should either use AES with an implicit padding declaration (see the available modes ) or force the length (in bytes) of data encrypted/decrypted to be a multiple of 16.

You should either use AES with an implicit padding declaration (see the available modes) or force the length (in bytes) of data encrypted/decrypted to be a multiple of 16. Also, by default, java uses ECB mode, which can be really unsecured depending on which type of data you are using, you should probably use a CBC mode.

I have changed the initline of the cipher to: cipher = Cipher. GetInstance("AES/CBC/PKCS5Padding"); But the same exception is thrown .. For getting the correct length I used the SHA-Hash - I think this should be enough. Moreover the first time I use the setup() method no exception is thrown – Frederik Apr 8 at 15:28 1 @Frederik: You have to understand how padding works: The padding mode will append some filling stuff to the plain text data before encrypting.

After decrypting, this padding is stripped off again. But to know how many bytes to strip off, the contents of the padding is important, and if we decrypted with a wrong key, the last some bytes are not in one of the formats which would get added by the padding algorithm. As said, use NoPadding, but then you'll have to make sure your data length is a multiple of the block length.

– PaÅ­lo Ebermann Apr 8 at 15:49 For the PKCS5Padding, it is the same as the one described in RFC 1423 for DES CBC. – PaÅ­lo Ebermann Apr 8 at 15:57 Sorry, I still don't get the Problem. My encrypted Data has a length of 32.

The block length is 16 isn't it? Is it a security gap, if I go on and let the cipher throw an exception if the length is invalid? – Frederik Apr 8 at 18:18.

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