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0auth_signature using SHA1-RSA in java

In have integrated oauth1.0. i am using sha1-rsa signature method. i have generated oauth signature. i got 200 status but i did not get any value in service provider. my doubt is signature generation. how to generate the oauth signature using sha1-rsa in java? i have mentioned link what am using.
`private static KeyPair getKeyPair() throws NoSuchAlgorithmException {
KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
kpg.initialize(1024, new SecureRandom());
return kpg.genKeyPair();
}`
public static String sign(PrivateKey privateKey) throws Exception {
Signature privateSignature = Signature.getInstance(" ");
privateSignature.initSign(privateKey);
//privateSignature.update(plainText.getBytes(UTF_8));
byte[] signature = privateSignature.sign();
System.out.println(Base64.encodeBase64String(signature));
return Base64.encodeBase64String(signature);
//encodeToString(signature);
}
thanks in advance,

Below snippets generate a valid signature, i.e. signs the input data using an RSA Private Key string i.e. creates a private key from contents of a .pkcs8 private key file. This is in Groovy (works with Java with minimal syntax changes:
import java.security.SignatureException;
import javax.crypto.Mac;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.security.Signature;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
//-------- generate RSA-SHA1 signature from request data
def encryptUsingRSASHA1(String data, String key) throws
java.security.SignatureException
{
String result
try {
// get an rsa_sha1 key from the raw key bytes
//SHA1withRSA
Signature signature = Signature.getInstance("SHA1withRSA");
signature.initSign(getPrivateKey(key));
signature.update(data.getBytes("UTF-8"));
byte[] rawRSAsigned = signature.sign();
result= rawRSAsigned.encodeBase64()
} catch (Exception e) {
throw new SignatureException("Failed to generate Signature : " +
e.getMessage());
}
return result
}
//get PrivateKey from key string
def getPrivateKey(String privateKey) throws NoSuchAlgorithmException,
InvalidKeySpecException {
String privateKeyPEM = privateKey.replace("-----BEGIN PRIVATE KEY-----\n",
"").replace("-----END PRIVATE KEY-----", "").replaceAll("\n","");
byte[] privateKeyBytes = privateKeyPEM.decodeBase64();
PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(privateKeyBytes);
KeyFactory kf = KeyFactory.getInstance("RSA");
return kf.generatePrivate(keySpec);
}

Decrypting String using rsa key

I've encoded a simple json data using RSA public key and now I'm trying to decode it. The encoding part was done via terminal and the decoding is being performed programmatically. To verify the integrity of the encrypted file, I decrypted it via terminal and it works just fine. Now that I'm trying to decrypt the file programmatically, I'm running into decrypting issues. I can read the private_key.pem file perfectly and pass it to Cipher for decrypting the encoded file, however upon doing this I get the following exception.
java.lang.ArrayIndexOutOfBoundsException: too much data for RSA block
at com.android.org.bouncycastle.jcajce.provider.asymmetric.rsa.CipherSpi.engineDoFinal(CipherSpi.java:457)
at javax.crypto.Cipher.doFinal(Cipher.java:1204)
at com.benchmark.openssl.RSADecryption.decipherString(RSADecryption.java:295)
at com.benchmark.openssl.RSADecryption.main(RSADecryption.java:263)
at com.benchmark.MainActivity$1.onComplete(MainActivity.java:157)
at io.reactivex.internal.operators.completable.CompletableObserveOn$ObserveOnCompletableObserver.run(CompletableObserveOn.java:90)
at io.reactivex.Scheduler$DisposeTask.run(Scheduler.java:463)
at io.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:66)
at io.reactivex.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:57)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:152)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:265)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at java.lang.Thread.run(Thread.java:841)
OpenSSL Commands used:
openssl genrsa -out priv_key.pem 2048
openssl rsa -pubout -in priv_key.pem -out pub_key.pem
openssl rsautl -encrypt -in userdata.json -out user_encrypted_with_pub_key -inkey pub_key.pem –pubin
openssl rsautl -decrypt -in user_encrypted_with_pub_key -inkey priv_key.pem --> This is what I'm trying to do programmatically.
Code:
import org.spongycastle.util.io.pem.PemObject;
import org.spongycastle.util.io.pem.PemReader;
import android.util.Base64;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.security.GeneralSecurityException;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Security;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
public static void main(String privateKeyPath, String encodedFilePath) throws FileNotFoundException,
IOException, NoSuchAlgorithmException, NoSuchProviderException {
Security.addProvider(new BouncyCastleProvider());
String encodedString = readFileAsString(encodedStringPath);
Timber.v("Encoded String: %s", encodedString);
KeyFactory factory = KeyFactory.getInstance("RSA", "BC");
try {
PrivateKey priv = generatePrivateKey(factory, privateKeyPath);
Timber.i(String.format("Instantiated private key: %s", priv));
decipherString(priv, encodedString);
} catch (InvalidKeySpecException e) {
e.printStackTrace();
}
}
private static PrivateKey generatePrivateKey(KeyFactory factory,
String filename) throws InvalidKeySpecException,
FileNotFoundException, IOException {
PemFile pemFile = new PemFile(filename, false);
byte[] content = pemFile.getPemObject().getContent();
PKCS8EncodedKeySpec privKeySpec = new PKCS8EncodedKeySpec(content);
return factory.generatePrivate(privKeySpec);
}
private static void decipherString(PrivateKey privateKey, String encodedStringData) {
byte[] dectyptedText = null;
try {
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, privateKey);
dectyptedText = cipher.doFinal(encodedStringData.getBytes()); <---- EXCEPTION HERE
Timber.w("Deciphered text is: %s", new String(dectyptedText));
}
catch (Exception e) {
e.printStackTrace();
}
}
static class PemFile {
private PemObject pemObject;
public PemFile(String filename, boolean isBase64) throws FileNotFoundException, IOException {
PemReader pemReader = new PemReader(new InputStreamReader(new FileInputStream(filename)));
try {
this.pemObject = pemReader.readPemObject();
}
catch (Exception e) {
e.printStackTrace();
}
finally {
pemReader.close();
}
}
public PemObject getPemObject() {
return pemObject;
}
}
userdata.json:
{
"username":"umer",
"password":"123456",
"pin" : "123"
}

I figured it out by some trial and error since I don't have much knowledge about openssl. Anyways the process for decrypting an encrypted file should be the following.
Terminal:
String -> (Encrypt) -> Encrypted String -> (convert to base64) -> EncryptedBase64EncodedString -> (Decrypt) -> Original String
Programmtically:
EncryptedBase64EncodedString -> (convert from base64 to normal string [Use Default parameters only! No Padding or other constants for decoding base64 string]) -> Pass private_key & decoded string to Cipher -> Profit.
The resultant code is:
import org.spongycastle.util.io.pem.PemObject;
import org.spongycastle.util.io.pem.PemReader;
import android.util.Base64;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.security.GeneralSecurityException;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Security;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.RSAPrivateCrtKeySpec;
import java.security.spec.X509EncodedKeySpec;
import javax.crypto.Cipher;
public static void main(String privateKeyPath, String publicKeyPath, String encodedStringPath, boolean isPublicKeyAndDataBase64) throws FileNotFoundException,
IOException, NoSuchAlgorithmException, NoSuchProviderException {
Security.addProvider(new BouncyCastleProvider());
String encodedString = readFileAsString(encodedStringPath);
if(isPublicKeyAndDataBase64) {
KeyFactory factory = KeyFactory.getInstance("RSA", "BC");
Timber.w("Encoded String converted from base64: %s", decodeBase64ToBytesa(encodedString));
try {
PrivateKey priv = generatePrivateKey(factory, privateKeyPath);
Timber.i(String.format("Instantiated private key: %s", priv));
decipherString(priv, decodeBase64ToBytesa(encodedString));
} catch (InvalidKeySpecException e) {
e.printStackTrace();
}
return;
}
else
Timber.w("Encoded String: %s", encodedString);
KeyFactory factory = KeyFactory.getInstance("RSA", "BC");
try {
PrivateKey priv = generatePrivateKey(factory, privateKeyPath);
Timber.i(String.format("Instantiated private key: %s", priv));
decipherString(priv, encodedString.getBytes());
PublicKey pub = generatePublicKey(factory, publicKeyPath);
Timber.i(String.format("Instantiated public key: %s", pub));
} catch (InvalidKeySpecException e) {
e.printStackTrace();
}
}
private static PrivateKey generatePrivateKey(KeyFactory factory,
String filename) throws InvalidKeySpecException,
FileNotFoundException, IOException {
PemFile pemFile = new PemFile(filename, false);
byte[] content = pemFile.getPemObject().getContent();
PKCS8EncodedKeySpec privKeySpec = new PKCS8EncodedKeySpec(content);
return factory.generatePrivate(privKeySpec);
}
private static PublicKey generatePublicKey(KeyFactory factory,
String filename) throws InvalidKeySpecException,
FileNotFoundException, IOException {
PemFile pemFile = new PemFile(filename, false);
byte[] content = pemFile.getPemObject().getContent();
X509EncodedKeySpec pubKeySpec = new X509EncodedKeySpec(content);
return factory.generatePublic(pubKeySpec);
}
private static void decipherString(PrivateKey privateKey, byte[] encodedStringData) {
byte[] dectyptedText = null;
try {
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, privateKey);
dectyptedText = cipher.doFinal(encodedStringData);
Timber.w("Deciphered text is: %s", new String(dectyptedText));
}
catch (Exception e) {
e.printStackTrace();
}
}
static class PemFile {
private PemObject pemObject;
public PemFile(String filename, boolean isBase64) throws FileNotFoundException, IOException {
PemReader pemReader = null;
if(isBase64) {
Timber.i("reading base64 encoded pem file. base64DecodedString: %s", decodeBase64(filename));
pemReader = new PemReader(new StringReader(decodeBase64(filename)));
}
else
pemReader = new PemReader(new InputStreamReader(
new FileInputStream(filename)));
try {
this.pemObject = pemReader.readPemObject();
}
catch (Exception e) {
e.printStackTrace();
}finally {
pemReader.close();
}
}
public PemObject getPemObject() {
return pemObject;
}
}

How to store and reuse keypair in Java?

I am wanting generate a keypair once and reuse it.
public static KeyPair generateKeyPair() throws Exception {
KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");
generator.initialize(2048, new SecureRandom());
KeyPair pair = generator.generateKeyPair();
return pair;
}
How do I go about this?

There is a bit of a problem here: Java's focus is almost entirely on TLS and the cryptography required to implement TLS. For TLS a private key and a certificate is required. So you get into a situation where you:
have to generate a (bogus) self signed certificate to go with your public key or;
have to find another way of storing the private key without a certificate.
However, with (2.) you quickly get a method that isn't very compatible. If you want to go that way, you could create a PKCS#8 encrypted private key that is encrypted using PBE / CBC.
So here's some code to create a self signed certificate and use that to store the key. Note the expiration date, you could set it to 100 years to be on the safe side (or you could actually do some key management).
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.KeyStore;
import java.security.KeyStore.Entry;
import java.security.KeyStore.PrivateKeyEntry;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.Provider;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.Security;
import java.security.UnrecoverableEntryException;
import java.security.cert.Certificate;
import java.security.cert.CertificateException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.util.Calendar;
import java.util.Date;
import org.bouncycastle.asn1.x500.X500Name;
import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo;
import org.bouncycastle.cert.X509CertificateHolder;
import org.bouncycastle.cert.X509v3CertificateBuilder;
import org.bouncycastle.cert.jcajce.JcaX509CertificateConverter;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.operator.ContentSigner;
import org.bouncycastle.operator.OperatorCreationException;
import org.bouncycastle.operator.jcajce.JcaContentSignerBuilder;
public class StoreKeyPair {
public static KeyPair generateKeyPair() throws Exception {
KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");
generator.initialize(2048, new SecureRandom());
KeyPair pair = generator.generateKeyPair();
return pair;
}
public static Certificate selfSign(KeyPair keyPair, String subjectDN)
throws OperatorCreationException, CertificateException, IOException
{
Provider bcProvider = new BouncyCastleProvider();
Security.addProvider(bcProvider);
long now = System.currentTimeMillis();
Date startDate = new Date(now);
X500Name dnName = new X500Name(subjectDN);
// Using the current timestamp as the certificate serial number
BigInteger certSerialNumber = new BigInteger(Long.toString(now));
Calendar calendar = Calendar.getInstance();
calendar.setTime(startDate);
// 1 Yr validity
calendar.add(Calendar.YEAR, 1);
Date endDate = calendar.getTime();
// Use appropriate signature algorithm based on your keyPair algorithm.
String signatureAlgorithm = "SHA256WithRSA";
SubjectPublicKeyInfo subjectPublicKeyInfo = SubjectPublicKeyInfo.getInstance(keyPair
.getPublic().getEncoded());
X509v3CertificateBuilder certificateBuilder = new X509v3CertificateBuilder(dnName,
certSerialNumber, startDate, endDate, dnName, subjectPublicKeyInfo);
ContentSigner contentSigner = new JcaContentSignerBuilder(signatureAlgorithm).setProvider(
bcProvider).build(keyPair.getPrivate());
X509CertificateHolder certificateHolder = certificateBuilder.build(contentSigner);
Certificate selfSignedCert = new JcaX509CertificateConverter()
.getCertificate(certificateHolder);
return selfSignedCert;
}
public static void main(String[] args) throws Exception {
KeyPair generatedKeyPair = generateKeyPair();
String filename = "test_gen_self_signed.pkcs12";
char[] password = "test".toCharArray();
storeToPKCS12(filename, password, generatedKeyPair);
KeyPair retrievedKeyPair = loadFromPKCS12(filename, password);
// you can validate by generating a signature and verifying it or by
// comparing the moduli by first casting to RSAPublicKey, e.g.:
RSAPublicKey pubKey = (RSAPublicKey) generatedKeyPair.getPublic();
RSAPrivateKey privKey = (RSAPrivateKey) retrievedKeyPair.getPrivate();
System.out.println(pubKey.getModulus().equals(privKey.getModulus()));
}
private static KeyPair loadFromPKCS12(String filename, char[] password)
throws KeyStoreException, NoSuchAlgorithmException, CertificateException,
FileNotFoundException, IOException, UnrecoverableEntryException {
KeyStore pkcs12KeyStore = KeyStore.getInstance("PKCS12");
try (FileInputStream fis = new FileInputStream(filename);) {
pkcs12KeyStore.load(fis, password);
}
KeyStore.ProtectionParameter param = new KeyStore.PasswordProtection(password);
Entry entry = pkcs12KeyStore.getEntry("owlstead", param);
if (!(entry instanceof PrivateKeyEntry)) {
throw new KeyStoreException("That's not a private key!");
}
PrivateKeyEntry privKeyEntry = (PrivateKeyEntry) entry;
PublicKey publicKey = privKeyEntry.getCertificate().getPublicKey();
PrivateKey privateKey = privKeyEntry.getPrivateKey();
return new KeyPair(publicKey, privateKey);
}
private static void storeToPKCS12(
String filename, char[] password,
KeyPair generatedKeyPair) throws KeyStoreException, IOException,
NoSuchAlgorithmException, CertificateException, FileNotFoundException,
OperatorCreationException {
Certificate selfSignedCertificate = selfSign(generatedKeyPair, "CN=owlstead");
KeyStore pkcs12KeyStore = KeyStore.getInstance("PKCS12");
pkcs12KeyStore.load(null, null);
KeyStore.Entry entry = new PrivateKeyEntry(generatedKeyPair.getPrivate(),
new Certificate[] { selfSignedCertificate });
KeyStore.ProtectionParameter param = new KeyStore.PasswordProtection(password);
pkcs12KeyStore.setEntry("owlstead", entry, param);
try (FileOutputStream fos = new FileOutputStream(filename)) {
pkcs12KeyStore.store(fos, password);
}
}
}
Note that I was too lazy to properly handle the exceptions.
This code uses a slightly altered version of this answer, see my comments for why I changed the code.
The public key can of course be stored separately as well. Just call getEncoded and store the resulting SubjectPublicKeyInfo structure.

Java RSA encrypted AES key

I have an RSA private key that I am trying to decrypt another files contents that has an AES key in it. So far all I can seem to get to return from the processes is jargon. Not really sure what I am doing wrong in the below code. I have looked on google and have seen this done at least a 100 different ways.
import java.io.*;
import java.io.IOException;
import java.security.KeyFactory;
import java.security.interfaces.RSAPrivateKey;
import java.security.GeneralSecurityException;
import java.security.spec.PKCS8EncodedKeySpec;
import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import org.apache.commons.codec.binary.Base64;
import org.apache.commons.io.FileUtils;
public class RsaEncryption {
private Cipher _pkCipher;
public RsaEncryption() throws GeneralSecurityException {
// create RSA public key cipher
_pkCipher = Cipher.getInstance("RSA");
}
public String loadKey(File in, String privateKey) throws GeneralSecurityException, IOException, Exception {
privateKey = privateKey.replaceAll("-+.*?-+", "");
byte[] encodedKey = Base64.decodeBase64(privateKey);
// create private key
PKCS8EncodedKeySpec privateKeySpec = new PKCS8EncodedKeySpec(encodedKey);
KeyFactory kf = KeyFactory.getInstance("RSA");
RSAPrivateKey pk = (RSAPrivateKey) kf.generatePrivate(privateKeySpec);
// read AES key
_pkCipher.init(Cipher.DECRYPT_MODE, pk);
byte[] encryptedBytes = FileUtils.readFileToByteArray(in);
ByteArrayInputStream fileIn = new ByteArrayInputStream(encryptedBytes);
CipherInputStream cis = new CipherInputStream(fileIn, _pkCipher);
DataInputStream dis = new DataInputStream(cis);
byte[] decryptedData = new byte[32];
dis.read(decryptedData);
String key = new String(decryptedData);
return key;
}
}
UPDATE
New way with bouncy castles pem converter still not working
import java.io.StringReader;
import java.io.File;
import java.io.IOException;
import java.security.KeyPair;
import java.security.interfaces.RSAPrivateKey;
import java.security.GeneralSecurityException;
import java.security.interfaces.RSAPublicKey;
import javax.crypto.Cipher;
import org.apache.commons.io.FileUtils;
import org.bouncycastle.openssl.PEMKeyPair;
import org.bouncycastle.openssl.PEMParser;
import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
public class RsaEncryption {
private Cipher _pkCipher;
private RSAPrivateKey _PrivateKey;
private RSAPublicKey _PublicKey;
public RsaEncryption(String privateKey) throws GeneralSecurityException, IOException {
loadKey(privateKey);
// create RSA public key cipher
_pkCipher = Cipher.getInstance("RSA/None/PKCS1Padding", "BC");
}
private void loadKey(String privateKey) throws IOException {
PEMParser pemParser = new PEMParser(new StringReader(privateKey));
PEMKeyPair pemKeyPair = (PEMKeyPair) pemParser.readObject();
JcaPEMKeyConverter converter = new JcaPEMKeyConverter().setProvider("BC");
KeyPair keyPair = converter.getKeyPair(pemKeyPair);
_PrivateKey = (RSAPrivateKey) keyPair.getPrivate();
_PublicKey = (RSAPublicKey) keyPair.getPublic();
pemParser.close();
}
public String decrypt(File in) throws GeneralSecurityException , IOException{
_pkCipher.init(Cipher.DECRYPT_MODE, _PrivateKey);
byte[] encryptedBytes = FileUtils.readFileToByteArray(in);
String key = new String(_pkCipher.doFinal(encryptedBytes));
System.out.println(key);
return key;
}
public RSAPrivateKey getPrivateKey() { return _PrivateKey; }
public RSAPublicKey getPublicKey() { return _PublicKey; }
}

RSA can only encrypt a small amount of data which must be processed as a chunk. You don't need a stream for that. Simply call
byte[] aesKey = _pkCipher.doFinal(FileUtils.readFileToByteArray(in));
to get the AES key.

JCE jars where in the wrong directory worked just fine once they got put in the correct directory.

RSA encryption(java) read the string input

I do RSA encryption and having a problem. I want to encrypt a string.To convert the string, I already have the rsHex array to convert it.. I run the source code but it give me error say "the system cannot find the file specified" Here is my source code. How do I solve his? Thanks for helping me :)
import de.flexiprovider.api.keys.PrivateKey;
import de.flexiprovider.api.keys.PublicKey;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.math.BigInteger;
import java.security.InvalidKeyException;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.RSAPrivateKeySpec;
import java.security.spec.RSAPublicKeySpec;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
public class RSA {
private String str, s;
private String chipertext;
private byte[] cipherData;
public RSA(String string) throws Exception {
try {
String input = string;
FileReader read = new FileReader(input);
BufferedReader reader = new BufferedReader(read);
while ((s = reader.readLine()) != null) {
byte[] theByteArray = s.getBytes();
setUserinput(string);
rsHex(theByteArray);
}
} catch (Exception ex) {
Logger.getLogger(RSA.class.getName()).log(Level.SEVERE, null, ex);
}
//Creating an RSA key pair in Java
KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA"); //instance of KeyPairGenerator
kpg.initialize(1024);//bit length of the modulus that required
KeyPair kp = kpg.genKeyPair();//returns a KeyPair object
Key publicKey = kp.getPublic(); //pull out the public and private keys
Key privateKey = kp.getPrivate();
//Saving the public and private key
//private key will be placed on our server, and the public key distributed to clients.
KeyFactory fact = KeyFactory.getInstance("RSA");
RSAPublicKeySpec pub = (RSAPublicKeySpec) fact.getKeySpec(publicKey, RSAPublicKeySpec.class);
RSAPrivateKeySpec priv = (RSAPrivateKeySpec) fact.getKeySpec(privateKey, RSAPrivateKeySpec.class);
// Save the file to local drive
saveToFile("c:\\public.key", pub.getModulus(), pub.getPublicExponent());
saveToFile("c:\\private.key", priv.getModulus(),priv.getPrivateExponent());
}
private void rsHex(byte[] bytes) throws Exception {
StringBuilder hex = new StringBuilder();
for (byte b : bytes) {
String hexString = Integer.toHexString(0x00FF & b);
hex.append(hexString.length() == 1 ? "0" + hexString : hexString);
}
setChipertext(hex.toString());
}
//save the moduli and exponents to file, we can just use boring old serialisation
public void saveToFile(String fileName, BigInteger mod, BigInteger exp) throws IOException {
FileOutputStream f = new FileOutputStream(fileName);
ObjectOutputStream oos = new ObjectOutputStream(f);
oos.writeObject(mod);
oos.writeObject(exp);
oos.close();
}
////Encryption
//initialise the cipher with the public key that we previously saved to file.
PublicKey readKeyFromFile(String keyFileName) throws IOException {
PublicKey key = null;
try {
FileInputStream fin = new FileInputStream(keyFileName);
ObjectInputStream ois = new ObjectInputStream(fin);
BigInteger m = (BigInteger) ois.readObject();
BigInteger e = (BigInteger) ois.readObject();
RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(m, e);
KeyFactory fact = KeyFactory.getInstance("RSA");
java.security.PublicKey pubKey = fact.generatePublic(keySpec);
ois.close();
}
catch (Exception e) {
e.printStackTrace();
}
return key;
}
public void rsaEncrypt(String str)throws Exception {
PublicKey pubKey = readKeyFromFile(str);
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE, pubKey);//initialise the cipher
cipherData = cipher.doFinal(str.getBytes());//passing in the data to be encrypted
rsHex(cipherData);
}
public String getUserinput() {
return str;
}
public String getChipertext() {
return chipertext;
}
public void setUserinput(String input) {
this.str = input;
}
public void setChipertext(String chipertext) throws Exception {
this.chipertext = chipertext;
}
}
----main Program------
import java.util.Scanner;
public class TWO{
public static void main(String[] args) throws Exception{
Scanner scan = new Scanner(System.in);
System.out.println("Insert your string");
String str = scan.nextLine();
RSA two = new RSA(str);
System.out.println("Encrypted: "+ two.getChipertext());
}
}

The problem is that you're taking an input string from the user, but then your code is treating this as though it was a filename by constructing a FileReader with that string.
Instead of all that nonsense with the FileReader and BufferedReader, is there any reason why you don't just use string.getBytes()?
You also seem to be making life awfully complicated for yourself: you're taking a string, converting into a byte array, then converting that into a string again (with hex representation), then converting that into a byte array again. That's an awful lot of messing about when you could really just take the byte representation of the original string (as given to you by getBytes()) and pass that directly to the RSA encryption.