How to convert Byte array to PrivateKey or PublicKey type?

Question

I am using RSA algorithm to generate public and private key

final KeyPairGenerator keyGen = KeyPairGenerator.getInstance(ALGORITHM);
keyGen.initialize(1024);
final KeyPair key = keyGen.generateKeyPair();
final PrivateKey privateKey=key.getPrivate();
final PublicKey publickey=key.getPublic();

after that these keys are encoded using Base64 encoder and save it into database.

How to convert this encoded String to Private and Public Key Type in java is to decrypt file. when decoding this String using Base64Decoder will get a byte array. how to convert this Byte array to public or private key type?

Solution

If you have a byte[] representing the output of getEncoded() on a key, you can use KeyFactory to turn that back into a PublicKey object or a PrivateKey object.

byte[] privateKeyBytes;
byte[] publicKeyBytes;
KeyFactory kf = KeyFactory.getInstance("RSA"); // or "EC" or whatever
PrivateKey privateKey = kf.generatePrivate(new PKCS8EncodedKeySpec(privateKeyBytes));
PublicKey publicKey = kf.generatePublic(new X509EncodedKeySpec(publicKeyBytes));

Comments

[Dean Blakely]

I've searched for 2 days to find how to convert RSA keys to strings and back and this is the ONLY post that has a working solution. Thanks nsayer!

[alper]

well you cannot give object name as "public" or "private".

[Wheezil]

Note that getEncoded() on a key doesn't tell you what is the encoding. The Key interface has getFormat(), which returns a string indicating the format, but then you have to know what class goes with each format. Seems like a standard ServiceLoader could help this?