How to convert BigInteger to String?

Question

I decrypted a data and got a BigInt and when I tried to convert it to string I got some Wired characters.

Code for getting BigInteger

BigInteger dec = process.Decrypt(sec);

Code for getting ByteArray

byte testBy[] = dec.toByteArray();

Code for Converting into String

String ss = new String(testBy);
System.out.println(ss);

and I tried this code too

String ss = new String(testBy);
System.out.println(ss, "UTF8");

I'm getting this output

=^ö½ß‡k+Éæ‚ûŽ3B‚+…Òæ?&¶?kÛUô—c

Help me out here..

why do you need the byte array? Just use BigInteger.toString() method — vefthym
– vefthym, Commented Feb 23, 2014 at 16:31
Pretty sure there is no println(String, String) method. Also, String ss = new String(testBy, "UTF-8"); would be acceptable. — Josh M
– Josh M, Commented Feb 23, 2014 at 16:35
What is process.Decrypt? Sure it returns a BigInteger, but if it is supposed to hold a String we will need more information about how this method actually stores data inside the BigInteger. Check its API documentation. — Anthony Accioly
– Anthony Accioly, Commented Feb 23, 2014 at 16:38
@AnthonyAccioly I'm trying an decryption of an encrypted data here is the code return c.modPow(lambda, nsquare).subtract(BigInteger.ONE).divide(n).multiply(u).mod(n); — SHiv
– SHiv, Commented Feb 23, 2014 at 16:45

Don Roby · Accepted Answer · 2014-02-23 16:29:53Z

16

BigInteger has a toString() method, which gives a decimal string representation of the value.

answered Feb 23, 2014 at 16:29

Don Roby

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5 Comments

Srinath Ganesh Over a year ago

NOTE : public String toString(int radix) ; else default value of 10

SHiv Over a year ago

@DonRoby so how can i convert that bigInt to original text. i mean decrypted text

Anthony Accioly Over a year ago

Sivashankar, you asked your question wrong. this is clearly a XY problem here. You don't want a String representing the number that the BigInteger holds. You want the decrypted text. And the answer is, we can't help you without knowing your library (there is a gazillion ways in which the decrypted data can be stored inside the BigInteger, plus another gazillion things that the data can really be).

SHiv Over a year ago

@AnthonyAccioly let me put in another way when i give a small data file the above code is working properly but if i gave a large data file it's showing that above output. Large means just a 20kb file.

Anthony Accioly Over a year ago

We still can't help you Sivas. The point is, you are asking for specific details of a implementation that we know nothing about. It can be a bug, there can be something missing, or it can be designed that way - we don't know. If this is code you own, debug the encryption process; if it is a library, read its documentations. If it is a popular / well known cryptography library ask a new question about "How can I decrypt my file using library XXX" and providing relevant details about how you have encrypted it.

barak manos · Accepted Answer · 2014-02-23 16:30:52Z

1

A call to System.out.println(dec) should print the decimal representation of dec correctly.

So just make sure that BigInteger dec = process.Decrypt(sec) yields the expected result.

answered Feb 23, 2014 at 16:30

barak manos

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Comments

Devavrata · Accepted Answer · 2014-02-23 16:37:55Z

0

toString() method convert BigInteger to String.Actually it overrides the Object toString() method.Or directly pass BigInteger object to System.out.println() because println bydefault takes Object.toString().

answered Feb 23, 2014 at 16:37

Devavrata

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