Write public/private key to the SharedPreferences and use it
android, private-key, public-key, sharedpreferences
Solution
Ok. I found some solution and change something. This is new class for public/private key storing and getting it again from stored string. This class works for me !
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.X509EncodedKeySpec;
import org.bouncycastle.util.encoders.Base64;
import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
public class KeyGenerator extends Activity{
SharedPreferences SP;
SharedPreferences.Editor SPE;
PublicKey pubKey;
PrivateKey privKey;
Context context;
public KeyGenerator(Context context){
this.context = context;
SP = context.getSharedPreferences("KeyPair", MODE_PRIVATE);
}
public void generateKeys(){
try {
KeyPairGenerator generator;
generator = KeyPairGenerator.getInstance("RSA", "BC");
generator.initialize(256, new SecureRandom());
KeyPair pair = generator.generateKeyPair();
pubKey = pair.getPublic();
privKey = pair.getPrivate();
byte[] publicKeyBytes = pubKey.getEncoded();
String pubKeyStr = new String(Base64.encode(publicKeyBytes));
byte[] privKeyBytes = privKey.getEncoded();
String privKeyStr = new String(Base64.encode(privKeyBytes));
SPE = SP.edit();
SPE.putString("PublicKey", pubKeyStr);
SPE.putString("PrivateKey", privKeyStr);
SPE.commit();
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (NoSuchProviderException e) {
e.printStackTrace();
}
}
public PublicKey getPublicKey(){
String pubKeyStr = SP.getString("PublicKey", "");
byte[] sigBytes = Base64.decode(pubKeyStr);
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(sigBytes);
KeyFactory keyFact = null;
try {
keyFact = KeyFactory.getInstance("RSA", "BC");
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (NoSuchProviderException e) {
e.printStackTrace();
}
try {
return keyFact.generatePublic(x509KeySpec);
} catch (InvalidKeySpecException e) {
e.printStackTrace();
}
return null;
}
public String getPublicKeyAsString(){
return SP.getString("PublicKey", "");
}
public PrivateKey getPrivateKey(){
String privKeyStr = SP.getString("PrivateKey", "");
byte[] sigBytes = Base64.decode(privKeyStr);
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(sigBytes);
KeyFactory keyFact = null;
try {
keyFact = KeyFactory.getInstance("RSA", "BC");
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (NoSuchProviderException e) {
e.printStackTrace();
}
try {
return keyFact.generatePrivate(x509KeySpec);
} catch (InvalidKeySpecException e) {
e.printStackTrace();
}
return null;
}
public String getPrivateKeyAsString(){
return SP.getString("PrivateKey", "");
}
}
Problem
I am trying to encrypt and decrypt a text with public/private keys.First of all, I create my keys and store them in sharedpreferences with this code : ``` SharedPreferences SP; SharedPreferences.Editor SPE; KeyPairGenerator keyGen; KeyPair keypair; PublicKey publicKey; PrivateKey privateKey; keyGen = KeyPairGenerator.getInstance("RSA"); keyGen.initialize(1024); keypair = keyGen.genKeyPair(); privateKey = keypair.getPrivate(); publicKey = keypair.getPublic(); SPE = SP.edit(); SPE.putString("PublicKey", publicKey.toString()); SPE.putString("PrivateKey", privateKey.toString()); SPE.commit(); ``` In my SharedPreferences file, keys are written like this : PublicKey: RSA Public Key modulus: d07b8f32968cf65301fd710f9d6d036feac01d7b98c92ff979cd324d252cb257ff48d6630b33f0f68bd0ee81c3a83502a0abf0b263dc96c2b86940f7ec19ab1865626383e55cf5a37e25ef4eb6ca88a39f31becb6065434bc2236177aa5b35266fe0379164faea6ef7a92812e7aa3ef5fc488c70ab085f5564f09c0f6e927b49 public exponent: 10001 PrivateKey: RSA Private CRT Key modulus: d07b8f32968cf65301fd710f9d6d036feac01d7b98c92ff979cd324d252cb257ff48d6630b33f0f68bd0ee81c3a83502a0abf0b263dc96c2b86940f7ec19ab1865626383e55cf5a37e25ef4eb6ca88a39f31becb6065434bc2236177aa5b35266fe0379164faea6ef7a92812e7aa3ef5fc488c70ab085f5564f09c0f6e927b49 public exponent: 10001 private exponent: 67ebef696c1a3fff0892e8f4bba8477a562e05844298a6cd58a5ac59401a939bc1a8f114d5d4c25c633d766640bd6c0f2f4005ef265022e6553e4220531448702e4bbf4322b9d5cf444d16eea151e5d565412b49208a73d9236607475d201affa21d374e3186f14b651b08565be4725f89fc6797a79c8433c4dd089589284a01 primeP: ee4ad1a56f4ee3b12c198d09b08a92c349f94cc79a6143ca7140fa64c919f2d9c24c29d3b413fdc4039000b6b5feac5a764ce436db4a4a382d8ceecbc768e0d1 primeQ: dff9a761807440b4a5a4fb04ebaa22849f6543f33168bd6e83b3c549b346661124d7879e168c1009e97c01b3fdcd7088eebd9c989b64d7c4b81ea46f9e06d0f9 primeExponentP: 2ce01e371f8d25c819dbfdf9932ba593ed7c6b7f338d99aca8436a644c92fc6f11ee31fa5271695adea8e1d986d09d38b40aaaf7c1b86dddc28645fa4e656be1 primeExponentQ: 21904af9fc82ef5362e3474ea4763978005eef80d92da5fd92b4f4e2a77fec39b378acf50ed1ec715fd0da7c7b9336c2fe6be1b4a8ccc2dcd2ee9c9bb165ba19 crtCoefficient: d8ccccb874ec4c2d464e84829547507e1ebf78e506caa77950b04329957b8713e80553874b825bf5c90b214984b4657b64965867460d87aab135f43930db48ec And with this code i am trying to read this keys : ``` private PublicKey getPublicKey() throws UnsupportedEncodingException, NoSuchAlgorithmException, InvalidKeySpecException{ byte[] keyBytes = Base64.decodeBase64(SP.getString("PublicKey", "default value").getBytes("utf-8")); X509EncodedKeySpec spec = new X509EncodedKeySpec(keyBytes); KeyFactory keyFactory = KeyFactory.getInstance("RSA"); PublicKey key = keyFactory.generatePublic(spec); return key;} ``` But something goes wrong.It gives InvalidKeySpecException. I thing this cannot read the keys from file.How can i fix this problem? Thank you.