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base64 decoding

Posted on 2004-08-25
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Last Modified: 2012-06-27
I am using the import w3c.tools.codec.Base64Decoder;

to decode a base64 string, the method
new Base64Decoder(base64string).processString() returns a string object I need a byte representation of this data.
Is it correct to assume that we jsut need to call getBytes() at the end?
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Question by:inzaghi
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18 Comments
 
LVL 35

Expert Comment

by:girionis
ID: 11894849
Yes, I would have thought that this is enough.

Regards
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LVL 86

Expert Comment

by:CEHJ
ID: 11894851
Yes. YOu must ask for thre correct encoding though
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Author Comment

by:inzaghi
ID: 11897497
Will I still need to do this even if when I open the file for reading the data from as

br = new BufferedReader( new InputStreamReader( f, "UTF-8)) );
String str = br.readLine();
String decode = new Base64Decoder(str.processString();
byte[] b = decode.getBytes();
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Author Comment

by:inzaghi
ID: 11897502
oops this refers to

>>Yes. YOu must ask for thre correct encoding though
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Expert Comment

by:CEHJ
ID: 11897538
Can you remind me how you've *written* the atoms?
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Author Comment

by:inzaghi
ID: 11897583
username + \u241e + encrypteddata

I have tokenized the string based on the u241e
and to get the encypteddata back into byte data I have done the above ( i haven't shown  the full solution above though)
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Expert Comment

by:CEHJ
ID: 11897717
>>( i haven't shown  the full solution above though)

Well that's what's confusing me! Can you do so (and repeat what your quesition is ;-))?
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Expert Comment

by:CEHJ
ID: 11897723
When i say 'the full solution' i mean the full code for handling that part of the reading back of course
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Author Comment

by:inzaghi
ID: 11897816
br = new BufferedReader( new InputStreamReader( f, "UTF-8)) );
while (str = br.readLine!=null){
 StringTokenizer st = new StringTokenizer(str, " \u241e");
 String user= st.nextToken();
 String base64 = st.nextToken();
String decodedS = new Base64Decoder(base64).processString();
byte[] b = decodedS.getBytes("UTF-8");
}                  }
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Expert Comment

by:CEHJ
ID: 11897893
In what way does processString work (i don't know the class)?
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LVL 86

Expert Comment

by:CEHJ
ID: 11897930
Forget that - i checked it. No - that call won't do as you originally had an encrypted byte array there, not a String, as far as i can remember
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Author Comment

by:inzaghi
ID: 11907663
sorry 4 the late reply,

I am trying to get the original encrypted byte array.

Originall the byte array was encoded to base64.
I know need to decode it and get the bytes.

Dont understand why the following will not work?
String decodedS = new Base64Decoder(base64).processString();
byte[] b = decodedS.getBytes("UTF-8");

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Author Comment

by:inzaghi
ID: 11907794
The actual string consists
of the username + seperator + encryptedData

The encrypted data is a byte array which has been encoded using base64

I don't understand why
String decodedS = new Base64Decoder(base64).processString();
byte[] b = decodedS.getBytes("UTF-8");


will not work?
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LVL 92

Accepted Solution

by:
objects earned 350 total points
ID: 11907970
you need something more like:

InputStream in = new ByteArrayInputStream(base64.getBytes("UTF-8"));
OutputStream out = new ByteArrayOutputStream();
new Base64Decoder(in, out).process();
in.close();
out.close();
byte[] encrypted = out.toByteArray();


told you life would be simpler if you avoided encoding altogether ;)
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Author Comment

by:inzaghi
ID: 11910815
Thanks objects, but why wont this work

String decodedS = new Base64Decoder(base64).processString();
byte[] b = decodedS.getBytes("UTF-8");
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LVL 86

Assisted Solution

by:CEHJ
CEHJ earned 150 total points
ID: 11910958
>>Thanks objects, but why wont this work

It's just that i'm a bit suspicious of how an array of 'binary' data is going to be handled as a String. It *may* be OK (and we can test it [more later]), but this:

>>byte[] b = decodedS.getBytes("UTF-8");

strikes me as wrong. Isn't what's being decoded at this point the encrypted data? If so, why is it being decrypted as UTF-8? It certainly won't *en*crypt properly in UTF-8. The array should have just been base64'd - nothing else
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Expert Comment

by:objects
ID: 11918379
> Thanks objects, but why wont this work

Cause there is additional encoding involved in converting between byte arrays and Strings which will corrupt your data.
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Expert Comment

by:CEHJ
ID: 11935221
8-)
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