Only RSAPrivate (Crt) KeySpec and PKCS8EncodedKeySpec supported for RSA private keys

问题:

I following the steps from the link : How to read .pem file to get private and public key. I executed the following three commands:

1. $openssl genrsa -out mykey.pem 2048 2. $openssl pkcs8 -topk8 -inform PEM -outform PEM -in mykey.pem -out private_key.pem -nocrypt 3. $ openssl rsa -in mykey.pem -pubout -outform DER -out public_key.der 

This created three files, but when I was trying to read those through Java code I started facing below error:

PUBLIC KEY EXPO : 65537 Only RSAPrivate(Crt)KeySpec and PKCS8EncodedKeySpec supported for RSA private keys 

My code for reference:

public class PublicPrivateKeyDemo {     private static File privateKeyFile = null;     private static File publicKeyFile = null;      public static void main(String[] args) {         String path = "C:/Users/test898/keys";         privateKeyFile = new File(path + "/" + "private.pem");         publicKeyFile = new File(path + "/" + "public.der");          try {             loadkeys();         } catch (IOException | GeneralSecurityException e) {             System.out.println(e.getMessage());         }     }      private static void loadkeys() throws IOException, GeneralSecurityException {         byte[] publicKeyBytes = new byte[(int) publicKeyFile.length()];         FileInputStream publicFis = null;         publicFis = new FileInputStream(publicKeyFile);         if (publicFis.read(publicKeyBytes) > 0) {             X509EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(publicKeyBytes);             KeyFactory factory = KeyFactory.getInstance("RSA");             RSAPublicKey pubKey = (RSAPublicKey) factory.generatePublic(publicKeySpec);             BigInteger pKeyModulus = pubKey.getModulus();             BigInteger pKeyExponent = pubKey.getPublicExponent();             System.out.println("PUBLIC KEY EXPO : "+pKeyExponent);          }          byte[] privateKeyBytes = new byte[(int) privateKeyFile.length()];         FileInputStream privateFis = null;         privateFis = new FileInputStream(privateKeyFile);         if (privateFis.read(privateKeyBytes) > 0) {             //PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(privateKeyBytes);             X509EncodedKeySpec spec = new X509EncodedKeySpec(privateKeyBytes);             KeyFactory keyFactory = KeyFactory.getInstance("RSA");             RSAPrivateKey privKey = (RSAPrivateKey) keyFactory.generatePrivate(spec);             BigInteger pKeyModulus = privKey.getModulus();             BigInteger pKeyExponent = privKey.getPrivateExponent();             System.out.println("PRIVATE KEY : "+pKeyExponent);         }      } } 

Please help me whats wrong here ? I assume Private Key should give value something simillar like below":

21150549370950609585296765828149303178265715265804890679831411170495636016527926323370428466362501818569080118374307191403222367256185274427528812911191842330928112748042350818573390540259857225467392220170770506599589136056049534085562156615813126185240565396115577449461468695709719589257257375788267753694280485882595576829517086782992300102288858453543505912425724874212273830247789870669315715724390578125469483751830964757980799543436412647956770560679365767737577100276745456138533646455249170660612983618544127693626739283128573829732806886889896396374650462743743148634276240986662548043510018342217214342529 

回答1:

As per the link :http://codeartisan.blogspot.in/2009/05/public-key-cryptography-in-java.html You should be trying the below

Generate a 2048-bit RSA private key

$ openssl genrsa -out private_key.pem 2048 

Convert 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 -nocrypt 

Output public key portion in DER format (so Java can read it)

$ openssl rsa -in private_key.pem -pubout -outform DER -out public_key.der 

You can read the java code like below:

import java.io.DataInputStream;     import java.io.File;     import java.io.FileInputStream;     import java.io.IOException;     import java.security.KeyFactory;     import java.security.NoSuchAlgorithmException;     import java.security.interfaces.RSAPrivateKey;     import java.security.interfaces.RSAPublicKey;     import java.security.spec.InvalidKeySpecException;     import java.security.spec.PKCS8EncodedKeySpec;     import java.security.spec.X509EncodedKeySpec;      public class Demo {          public static final String PRIVATE_KEY="/home/user/private.der";         public static final String PUBLIC_KEY="/home/user/public.der";          public static void main(String[] args) throws IOException, NoSuchAlgorithmException, InvalidKeySpecException {             //get the private key             File file = new File(PRIVATE_KEY);             FileInputStream fis = new FileInputStream(file);             DataInputStream dis = new DataInputStream(fis);              byte[] keyBytes = new byte[(int) file.length()];             dis.readFully(keyBytes);             dis.close();              PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(keyBytes);             KeyFactory kf = KeyFactory.getInstance("RSA");             RSAPrivateKey privKey = (RSAPrivateKey) kf.generatePrivate(spec);             System.out.println("Exponent :" + privKey.getPrivateExponent());             System.out.println("Modulus" + privKey.getModulus());              //get the public key             File file1 = new File(PUBLIC_KEY);             FileInputStream fis1 = new FileInputStream(file1);             DataInputStream dis1 = new DataInputStream(fis1);             byte[] keyBytes1 = new byte[(int) file1.length()];             dis1.readFully(keyBytes1);             dis1.close();              X509EncodedKeySpec spec1 = new X509EncodedKeySpec(keyBytes1);             KeyFactory kf1 = KeyFactory.getInstance("RSA");             RSAPublicKey pubKey = (RSAPublicKey) kf1.generatePublic(spec1);              System.out.println("Exponent :" + pubKey.getPublicExponent());             System.out.println("Modulus" + pubKey.getModulus());         }     } 

Program Output:

PUBLIC KEY EXPO : 65537 PRIVATE KEY : 16540425323481903232154296082061217323015064904150073221896716535825697862890781586244035403066600439504989225032100277459509106847714925918656002207273016950425690931486784061794302602299415224979080443644674838230854689682941689891752703570749249869153966528967635783430367525635094847999700308350727275663213969614628360232440655477057807291869565586695953970804798770095849408924111596670565606097668752646013504502815936286143578191877967720393294592625997337105475883689954727277867955887242546330469781268095607005541678733388864537898085207735975487415418212440417692928205650585590564551063589766600954407329 

文章来源: Only RSAPrivate (Crt) KeySpec and PKCS8EncodedKeySpec supported for RSA private keys