Load RSA public key from file
This program is doing almost everything with Public and private keys. The der format can be obtained but saving raw data ( without encoding base64). I hope this helps programmers.
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.SignatureException;
import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;
import sun.security.pkcs.PKCS8Key;
import sun.security.pkcs10.PKCS10;
import sun.security.x509.X500Name;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
/**
* @author Desphilboy
* DorOd bar shomA barobach
*
*/
public class csrgenerator {
private static PublicKey publickey= null;
private static PrivateKey privateKey=null;
//private static PKCS8Key privateKey=null;
private static KeyPairGenerator kpg= null;
private static ByteArrayOutputStream bs =null;
private static csrgenerator thisinstance;
private KeyPair keypair;
private static PKCS10 pkcs10;
private String signaturealgorithm= "MD5WithRSA";
public String getSignaturealgorithm() {
return signaturealgorithm;
}
public void setSignaturealgorithm(String signaturealgorithm) {
this.signaturealgorithm = signaturealgorithm;
}
private csrgenerator() {
try {
kpg = KeyPairGenerator.getInstance("RSA");
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
System.out.print("No such algorithm RSA in constructor csrgenerator\n");
}
kpg.initialize(2048);
keypair = kpg.generateKeyPair();
publickey = keypair.getPublic();
privateKey = keypair.getPrivate();
}
/** Generates a new key pair
*
* @param int bits
* this is the number of bits in modulus must be 512, 1024, 2048 or so on
*/
public KeyPair generateRSAkys(int bits)
{
kpg.initialize(bits);
keypair = kpg.generateKeyPair();
publickey = keypair.getPublic();
privateKey = keypair.getPrivate();
KeyPair dup= keypair;
return dup;
}
public static csrgenerator getInstance() {
if (thisinstance == null)
thisinstance = new csrgenerator();
return thisinstance;
}
/**
* Returns a CSR as string
* @param cn Common Name
* @param OU Organizational Unit
* @param Org Organization
* @param LocName Location name
* @param Statename State/Territory/Province/Region
* @param Country Country
* @return returns csr as string.
* @throws Exception
*/
public String getCSR(String commonname, String organizationunit, String organization,String localname, String statename, String country ) throws Exception {
byte[] csr = generatePKCS10(commonname, organizationunit, organization, localname, statename, country,signaturealgorithm);
return new String(csr);
}
/** This function generates a new Certificate
* Signing Request.
*
* @param CN
* Common Name, is X.509 speak for the name that distinguishes
* the Certificate best, and ties it to your Organization
* @param OU
* Organizational unit
* @param O
* Organization NAME
* @param L
* Location
* @param S
* State
* @param C
* Country
* @return byte stream of generated request
* @throws Exception
*/
private static byte[] generatePKCS10(String CN, String OU, String O,String L, String S, String C,String sigAlg) throws Exception {
// generate PKCS10 certificate request
pkcs10 = new PKCS10(publickey);
Signature signature = Signature.getInstance(sigAlg);
signature.initSign(privateKey);
// common, orgUnit, org, locality, state, country
//X500Name(String commonName, String organizationUnit,String organizationName,Local,State, String country)
X500Name x500Name = new X500Name(CN, OU, O, L, S, C);
pkcs10.encodeAndSign(x500Name,signature);
bs = new ByteArrayOutputStream();
PrintStream ps = new PrintStream(bs);
pkcs10.print(ps);
byte[] c = bs.toByteArray();
try {
if (ps != null)
ps.close();
if (bs != null)
bs.close();
} catch (Throwable th) {
}
return c;
}
public PublicKey getPublicKey() {
return publickey;
}
/**
* @return
*/
public PrivateKey getPrivateKey() {
return privateKey;
}
/**
* saves private key to a file
* @param filename
*/
public void SavePrivateKey(String filename)
{
PKCS8EncodedKeySpec pemcontents=null;
pemcontents= new PKCS8EncodedKeySpec( privateKey.getEncoded());
PKCS8Key pemprivatekey= new PKCS8Key( );
try {
pemprivatekey.decode(pemcontents.getEncoded());
} catch (InvalidKeyException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
File file=new File(filename);
try {
file.createNewFile();
FileOutputStream fos=new FileOutputStream(file);
fos.write(pemprivatekey.getEncoded());
fos.flush();
fos.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
/**
* Saves Certificate Signing Request to a file;
* @param filename is a String containing full path to the file which will be created containing the CSR.
*/
public void SaveCSR(String filename)
{
FileOutputStream fos=null;
PrintStream ps=null;
File file;
try {
file = new File(filename);
file.createNewFile();
fos = new FileOutputStream(file);
ps= new PrintStream(fos);
}catch (IOException e)
{
System.out.print("\n could not open the file "+ filename);
}
try {
try {
pkcs10.print(ps);
} catch (SignatureException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
ps.flush();
ps.close();
} catch (IOException e) {
// TODO Auto-generated catch block
System.out.print("\n cannot write to the file "+ filename);
e.printStackTrace();
}
}
/**
* Saves both public key and private key to file names specified
* @param fnpub file name of public key
* @param fnpri file name of private key
* @throws IOException
*/
public static void SaveKeyPair(String fnpub,String fnpri) throws IOException {
// Store Public Key.
X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(
publickey.getEncoded());
FileOutputStream fos = new FileOutputStream(fnpub);
fos.write(x509EncodedKeySpec.getEncoded());
fos.close();
// Store Private Key.
PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(privateKey.getEncoded());
fos = new FileOutputStream(fnpri);
fos.write(pkcs8EncodedKeySpec.getEncoded());
fos.close();
}
/**
* Reads a Private Key from a pem base64 encoded file.
* @param filename name of the file to read.
* @param algorithm Algorithm is usually "RSA"
* @return returns the privatekey which is read from the file;
* @throws Exception
*/
public PrivateKey getPemPrivateKey(String filename, String algorithm) throws Exception {
File f = new File(filename);
FileInputStream fis = new FileInputStream(f);
DataInputStream dis = new DataInputStream(fis);
byte[] keyBytes = new byte[(int) f.length()];
dis.readFully(keyBytes);
dis.close();
String temp = new String(keyBytes);
String privKeyPEM = temp.replace("-----BEGIN PRIVATE KEY-----", "");
privKeyPEM = privKeyPEM.replace("-----END PRIVATE KEY-----", "");
//System.out.println("Private key\n"+privKeyPEM);
BASE64Decoder b64=new BASE64Decoder();
byte[] decoded = b64.decodeBuffer(privKeyPEM);
PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(decoded);
KeyFactory kf = KeyFactory.getInstance(algorithm);
return kf.generatePrivate(spec);
}
/**
* Saves the private key to a pem file.
* @param filename name of the file to write the key into
* @param key the Private key to save.
* @return String representation of the pkcs8 object.
* @throws Exception
*/
public String SavePemPrivateKey(String filename) throws Exception {
PrivateKey key=this.privateKey;
File f = new File(filename);
FileOutputStream fos = new FileOutputStream(f);
DataOutputStream dos = new DataOutputStream(fos);
byte[] keyBytes = key.getEncoded();
PKCS8Key pkcs8= new PKCS8Key();
pkcs8.decode(keyBytes);
byte[] b=pkcs8.encode();
BASE64Encoder b64=new BASE64Encoder();
String encoded = b64.encodeBuffer(b);
encoded= "-----BEGIN PRIVATE KEY-----\r\n" + encoded + "-----END PRIVATE KEY-----";
dos.writeBytes(encoded);
dos.flush();
dos.close();
//System.out.println("Private key\n"+privKeyPEM);
return pkcs8.toString();
}
/**
* Saves a public key to a base64 encoded pem file
* @param filename name of the file
* @param key public key to be saved
* @return string representation of the pkcs8 object.
* @throws Exception
*/
public String SavePemPublicKey(String filename) throws Exception {
PublicKey key=this.publickey;
File f = new File(filename);
FileOutputStream fos = new FileOutputStream(f);
DataOutputStream dos = new DataOutputStream(fos);
byte[] keyBytes = key.getEncoded();
BASE64Encoder b64=new BASE64Encoder();
String encoded = b64.encodeBuffer(keyBytes);
encoded= "-----BEGIN PUBLIC KEY-----\r\n" + encoded + "-----END PUBLIC KEY-----";
dos.writeBytes(encoded);
dos.flush();
dos.close();
//System.out.println("Private key\n"+privKeyPEM);
return encoded.toString();
}
/**
* reads a public key from a file
* @param filename name of the file to read
* @param algorithm is usually RSA
* @return the read public key
* @throws Exception
*/
public PublicKey getPemPublicKey(String filename, String algorithm) throws Exception {
File f = new File(filename);
FileInputStream fis = new FileInputStream(f);
DataInputStream dis = new DataInputStream(fis);
byte[] keyBytes = new byte[(int) f.length()];
dis.readFully(keyBytes);
dis.close();
String temp = new String(keyBytes);
String publicKeyPEM = temp.replace("-----BEGIN PUBLIC KEY-----\n", "");
publicKeyPEM = publicKeyPEM.replace("-----END PUBLIC KEY-----", "");
BASE64Decoder b64=new BASE64Decoder();
byte[] decoded = b64.decodeBuffer(publicKeyPEM);
X509EncodedKeySpec spec =
new X509EncodedKeySpec(decoded);
KeyFactory kf = KeyFactory.getInstance(algorithm);
return kf.generatePublic(spec);
}
public static void main(String[] args) throws Exception {
csrgenerator gcsr = csrgenerator.getInstance();
gcsr.setSignaturealgorithm("SHA512WithRSA");
System.out.println("Public Key:\n"+gcsr.getPublicKey().toString());
System.out.println("Private Key:\nAlgorithm: "+gcsr.getPrivateKey().getAlgorithm().toString());
System.out.println("Format:"+gcsr.getPrivateKey().getFormat().toString());
System.out.println("To String :"+gcsr.getPrivateKey().toString());
System.out.println("GetEncoded :"+gcsr.getPrivateKey().getEncoded().toString());
BASE64Encoder encoder= new BASE64Encoder();
String s=encoder.encodeBuffer(gcsr.getPrivateKey().getEncoded());
System.out.println("Base64:"+s+"\n");
String csr = gcsr.getCSR( "[email protected]","baxshi az xodam", "Xodam","PointCook","VIC" ,"AU");
System.out.println("CSR Request Generated!!");
System.out.println(csr);
gcsr.SaveCSR("c:\\testdir\\javacsr.csr");
String p=gcsr.SavePemPrivateKey("c:\\testdir\\java_private.pem");
System.out.print(p);
p=gcsr.SavePemPublicKey("c:\\testdir\\java_public.pem");
privateKey= gcsr.getPemPrivateKey("c:\\testdir\\java_private.pem", "RSA");
BASE64Encoder encoder1= new BASE64Encoder();
String s1=encoder1.encodeBuffer(gcsr.getPrivateKey().getEncoded());
System.out.println("Private Key in Base64:"+s1+"\n");
System.out.print(p);
}
}
Below is the relevant information from the link which Zaki provided.
Generate a 2048-bit RSA private key
$ openssl genrsa -out private_key.pem 2048Convert private Key to PKCS#8 format (so Java can read it)
$ openssl pkcs8 -topk8 -inform PEM -outform DER -in private_key.pem -out private_key.der -nocryptOutput public key portion in DER format (so Java can read it)
$ openssl rsa -in private_key.pem -pubout -outform DER -out public_key.der
Private key
import java.nio.file.*;
import java.security.*;
import java.security.spec.*;
public class PrivateKeyReader {
public static PrivateKey get(String filename)
throws Exception {
byte[] keyBytes = Files.readAllBytes(Paths.get(filename));
PKCS8EncodedKeySpec spec =
new PKCS8EncodedKeySpec(keyBytes);
KeyFactory kf = KeyFactory.getInstance("RSA");
return kf.generatePrivate(spec);
}
}
Public key
import java.nio.file.*;
import java.security.*;
import java.security.spec.*;
public class PublicKeyReader {
public static PublicKey get(String filename)
throws Exception {
byte[] keyBytes = Files.readAllBytes(Paths.get(filename));
X509EncodedKeySpec spec =
new X509EncodedKeySpec(keyBytes);
KeyFactory kf = KeyFactory.getInstance("RSA");
return kf.generatePublic(spec);
}
}