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Should implement the solution with JCE I Have a Public Key String generated using the KeyPairGenerator.

How do I load this in openSSL Api call using PEM_read_bio_RSAPublicKey? Or this will have the x509 spec encoded how do we remove and generate the public which is compatible with the openssl api call?

try { // Get the public/private key pair KeyPairGenerator keyGen = KeyPairGenerator .getInstance(keyAlgorithm); keyGen.initialize(numBits); KeyPair keyPair = keyGen.genKeyPair(); PrivateKey privateKey = keyPair.getPrivate(); PublicKey publicKey = keyPair.getPublic(); System.out.println("\n" + "Generating key/value pair using " + privateKey.getAlgorithm() + " algorithm"); // Get the bytes of the public and private keys privateKeyBytes = privateKey.getEncoded(); publicKeyBytes = publicKey.getEncoded(); try { rsa_publickey = new BASE64Encoder().encodeBuffer((keyPair.getPublic()).getEncoded()); } catch(Exception e1) { e1.printStackTrace(); } System.out.println("PublicKey :"+rsa_publickey); } catch(Exception e1) { e1.printStackTrace(); }
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Perhaps you could try to export it from Java to the PEM format OpenSSL can read, using Bouncycastle's PEMWriter.

EDIT: For example, the following code:

KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA"); keyGen.initialize(2048); KeyPair keyPair = keyGen.genKeyPair(); PrivateKey privateKey = keyPair.getPrivate(); PublicKey publicKey = keyPair.getPublic(); // Solution 1: using BouncyCastle's PEMWriter PEMWriter pemWriter = new PEMWriter(new PrintWriter(System.out)); pemWriter.writeObject(publicKey); pemWriter.flush(); // Solution 2: using sun.misc.BASE64Encoder // (and possibly naive 64-character line split) sun.misc.BASE64Encoder encoder = new sun.misc.BASE64Encoder(); String encoded = encoder.encode(publicKey.getEncoded()); encoded = encoded.replace("\n", ""); StringBuilder builder = new StringBuilder(); builder.append("-----BEGIN PUBLIC KEY-----"); builder.append("\n"); int i = 0; while (i < encoded.length()) { builder.append(encoded.substring(i, Math.min(i + 64, encoded.length()))); builder.append("\n"); i += 64; } builder.append("-----END PUBLIC KEY-----"); System.out.println(builder);

produces this output:

-----BEGIN PUBLIC KEY----- MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA0CCQ5fdVEEm8u1CrbMXa FK35/d5MxNjCg7EQZwKsydRhfGhbK+u+iTUiv9rkqhcCucqrMi9eXtqt/QNGreFF oR5auneeCMgqnXxoX7wjuZ5DBt6qN6ZSe+sAPqSKbvvLUmpBUK9pdOvxegQFGG2d OUCcQLg2o6vLr9r7ZJDSxdyzCb14i+TEt0TnLjFTkR846dmX41gfU7eacoPxYWoo Pvhq2huyH0cP8rNJ2/+2BcInjyv5TpLT+m0lYjMar6exgonqRetIJF0Gi7unM+0V RsBoaBMAsLeqoR5OrCrSKepWbjixjHRMmjBaTYM5wP8DAbjVupUQ9kUwqRTzHTti XQIDAQAB -----END PUBLIC KEY----- -----BEGIN PUBLIC KEY----- MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA0CCQ5fdVEEm8u1CrbMXa FK35/d5MxNjCg7EQZwKsydRhfGhbK+u+iTUiv9rkqhcCucqrMi9eXtqt/QNGreFF oR5auneeCMgqnXxoX7wjuZ5DBt6qN6ZSe+sAPqSKbvvLUmpBUK9pdOvxegQFGG2d OUCcQLg2o6vLr9r7ZJDSxdyzCb14i+TEt0TnLjFTkR846dmX41gfU7eacoPxYWoo Pvhq2huyH0cP8rNJ2/+2BcInjyv5TpLT+m0lYjMar6exgonqRetIJF0Gi7unM+0V RsBoaBMAsLeqoR5OrCrSKepWbjixjHRMmjBaTYM5wP8DAbjVupUQ9kUwqRTzHTti XQIDAQAB -----END PUBLIC KEY-----

(If you want to do it without BouncyCastle, you might want to use another base 64 encoder, since it's usually not recommended to use sun.* packages that may not be exposed or available on all JREs.)

I haven't tried to load in using OpenSSL's API, but with OpenSSL on the command line, when you paste the above key, you get this (note that what's between the BEGIN/END delimiters is stdin, pasted on the terminal here):

$ openssl rsa -inform PEM -pubin -text -noout -----BEGIN PUBLIC KEY----- MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA0CCQ5fdVEEm8u1CrbMXa FK35/d5MxNjCg7EQZwKsydRhfGhbK+u+iTUiv9rkqhcCucqrMi9eXtqt/QNGreFF oR5auneeCMgqnXxoX7wjuZ5DBt6qN6ZSe+sAPqSKbvvLUmpBUK9pdOvxegQFGG2d OUCcQLg2o6vLr9r7ZJDSxdyzCb14i+TEt0TnLjFTkR846dmX41gfU7eacoPxYWoo Pvhq2huyH0cP8rNJ2/+2BcInjyv5TpLT+m0lYjMar6exgonqRetIJF0Gi7unM+0V RsBoaBMAsLeqoR5OrCrSKepWbjixjHRMmjBaTYM5wP8DAbjVupUQ9kUwqRTzHTti XQIDAQAB -----END PUBLIC KEY----- Modulus (2048 bit): 00:d0:20:90:e5:f7:55:10:49:bc:bb:50:ab:6c:c5: da:14:ad:f9:fd:de:4c:c4:d8:c2:83:b1:10:67:02: ac:c9:d4:61:7c:68:5b:2b:eb:be:89:35:22:bf:da: e4:aa:17:02:b9:ca:ab:32:2f:5e:5e:da:ad:fd:03: 46:ad:e1:45:a1:1e:5a:ba:77:9e:08:c8:2a:9d:7c: 68:5f:bc:23:b9:9e:43:06:de:aa:37:a6:52:7b:eb: 00:3e:a4:8a:6e:fb:cb:52:6a:41:50:af:69:74:eb: f1:7a:04:05:18:6d:9d:39:40:9c:40:b8:36:a3:ab: cb:af:da:fb:64:90:d2:c5:dc:b3:09:bd:78:8b:e4: c4:b7:44:e7:2e:31:53:91:1f:38:e9:d9:97:e3:58: 1f:53:b7:9a:72:83:f1:61:6a:28:3e:f8:6a:da:1b: b2:1f:47:0f:f2:b3:49:db:ff:b6:05:c2:27:8f:2b: f9:4e:92:d3:fa:6d:25:62:33:1a:af:a7:b1:82:89: ea:45:eb:48:24:5d:06:8b:bb:a7:33:ed:15:46:c0: 68:68:13:00:b0:b7:aa:a1:1e:4e:ac:2a:d2:29:ea: 56:6e:38:b1:8c:74:4c:9a:30:5a:4d:83:39:c0:ff: 03:01:b8:d5:ba:95:10:f6:45:30:a9:14:f3:1d:3b: 62:5d Exponent: 65537 (0x10001)

EDIT: If you want to export something within the BEGIN RSA PUBLIC KEY instead, you can try something like this:

RSAPublicKey rsaPublicKey = (RSAPublicKey) publicKey; RSAPublicKeyStructure pubkeyStruct = new RSAPublicKeyStructure( rsaPublicKey.getModulus(), rsaPublicKey.getPublicExponent()); pubkeyStruct.getDEREncoded(); // base64-encode this between the delimiters
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11 Comments

Can you please suggest using JCE
@MSSV, I've just added an example, I'm not sure if it's what you're looking for.
is there any encoding change if the header says as BEGIN RSA PUBLIC KEY instead of BEGIN PUBLIC KEY ?
@MSSV, yes. they are different, what's within BEGIN RSA PUBLIC KEY is the "subjectPublicKey" in this ASN.1 structure SubjectPublicKeyInfo := SEQUENCE { algorithm AlgorithmIdentifier, subjectPublicKey BIT STRING } whereas what's within BEGIN PUBLIC KEY is the whole structure (including AlgorithmIdentifier).
Then how do i set this using the bouncy castle?
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