Java Windows-1252 wrong chars

Question

I'm coding a RSA algorithm to encrypt a string to send to a VisualBasic webservice. Unfortunatelly the VB RSAcryptoserviceprovider always gives me an exception "Bad data" and i this the problem is the encoding. The VisualBasic code receives the string and converts it to a byte array using windows-1252 encoding and them decrypts it.

In my Java code i'm encrypting using this:

private static String encryptBlock(Cipher cipher, String textToEncrypt) {
    cipher.init(Cipher.ENCRYPT_MODE, pubKey);
    String encrypted = new String(cipher.doFinal(textToEncrypt.getBytes(Charset.defaultCharset())), "windows-1252");
    return encrypted;
}

When i 'system.out.print' the encrypted string it gives me strange chars like �. Does it means that me windows-1252 encoding is wrong right? What am i doing wrong here? Note that i can only make changes to the Java code and not the VB.

Thank you!

I don't believe Windows-1252 contains the � character - it's probably encoded in UTF-8 or UTF-16. — JonK, Nov 07 '14 at 11:02
'new String(cipher.doFinal(textToEncrypt.getBytes(Charset.defaultCharset())), "windows-1252");' if i print this it gives me some � characters — DiogoPinheiro, Nov 07 '14 at 11:08
So specify a different character set and see if the output changes. — JonK, Nov 07 '14 at 11:09
The output is always different because its a RSA cypher. But with UTF-8 and UTF-16 the � char is always showing up. — DiogoPinheiro, Nov 07 '14 at 11:13

score 2 · Accepted Answer · answered Nov 07 '14 at 11:48

2

You need to convert the ciphertext to base 64 encoding, and back to bytes before decrypting. Either that or you need to keep treating the ciphertext as binary.

There are no character encodings that will use every possible random byte value as printable character. So using just the default character encoding as you do now is going to lead to data loss.

When data is lost you will get an exception indicating that the size of the ciphertext is incorrect, or that the padding used within the RSA encryption is invalid.

answered Nov 07 '14 at 11:48

Maarten Bodewes

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But the VisualBasic code is expecting a string with 128 chars and windows-1252 encoding. And that Base 64 returns a 172 chars length. – DiogoPinheiro Nov 07 '14 at 11:54
You either make sure those characters are directly mapped to bytes, or you fix the VB code. There is no way around this. – Maarten Bodewes Nov 07 '14 at 11:55
How do you enter the VB string? – Maarten Bodewes Nov 07 '14 at 12:02
What do you mean by 'enter the VB string'? – DiogoPinheiro Nov 07 '14 at 12:06
Well, the ciphertext has to be stored/retrieved or otherwise communicated from the Java code to the VB code... – Maarten Bodewes Nov 07 '14 at 12:08
What intricates me is that a have a VB encryption program that uses exactly this same principle of encoding and it works. – DiogoPinheiro Nov 07 '14 at 12:08
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/64493/discussion-between-owlstead-and-diogopinheiro). – Maarten Bodewes Nov 07 '14 at 12:08
In the Java part i use URLEncoder to encode the encrypted string and then a send it via webservices. In the VB webservices it URLDecodes it and try to decrypt. – DiogoPinheiro Nov 07 '14 at 12:10

Java Windows-1252 wrong chars

1 Answers1