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javasecurityrsabouncycastlepkcs#8

Failed to parse RSA publicKey in Java

I am using the following code block to parse any RSA public key to encrypt.

    static byte[] encrypt(byte[] publicKey, byte[] inputData) throws Exception {

    PublicKey key = KeyFactory.getInstance(ALGORITHM).generatePublic(new X509EncodedKeySpec(publicKey));

    Cipher cipher = Cipher.getInstance(ALGORITHM);
    cipher.init(Cipher.ENCRYPT_MODE, key);

    byte[] encryptedBytes = cipher.doFinal(inputData);

    return encryptedBytes;
}

public static String getEncrypted(String data, String key) throws Exception {
    byte[] keyBytes = Base64.getDecoder().decode(key);
    return new String(Base64.getEncoder().encode(encrypt(keyBytes, data.getBytes())));
}

But for the following RSA public Key

MIIBCgKCAQEAs6YyGDXibkazM7QSeFBXjkAn5A8P87k+nuU6v5+zLJiD1KwkZ/SYnLwVSluOx19AzPHj07abDTJtthKtKpp2997UiV4CNUSzkZM1Eorf1+iLFhqeOiz9J5tYfFkKN5qPzwoPK4aFz35hQi7R1ORF9rFDPL+Ex79Tc+ABQF/CH5tn/NTXCNUYzLezg2Y1VOZGNhxd2LIv/29ZDxpJS8dD34H20HMMZCMGGolTXUIxVKI3cR0d1XzNCvAx3jcSkEUEPPH0lfusXqQOfCxJSIjorAzi5ucaWicvXYq6BNGulPqLoGBZnJ4HrFQF0oq1SU4i60VHqOgoiqMPQ+8cyjFBHQIDAQAB

while parsing I am getting the following exception

Caused by: java.security.spec.InvalidKeySpecException: java.security.InvalidKeyException: IOException: algid parse error, not a sequence
    at sun.security.rsa.RSAKeyFactory.engineGeneratePublic(RSAKeyFactory.java:205)
    at java.security.KeyFactory.generatePublic(KeyFactory.java:334)
Caused by: java.security.InvalidKeyException: IOException: algid parse error, not a sequence
    at sun.security.x509.X509Key.decode(X509Key.java:397)
    at sun.security.x509.X509Key.decode(X509Key.java:402)
    at sun.security.rsa.RSAPublicKeyImpl.<init>(RSAPublicKeyImpl.java:86)
    at sun.security.rsa.RSAKeyFactory.generatePublic(RSAKeyFactory.java:298)
    at sun.security.rsa.RSAKeyFactory.engineGeneratePublic(RSAKeyFactory.java:201)

Any idea what is failing and how to make a generic RSA public key parsing code.

Solution

  • Your problem is analagous to the problem in InvalidKeySpecException : algid parse error, not a sequence, though not the same. Just like PKCS8 is a generic format for private keys in (almost) any algorithm, by containing both an AlgorithmIdentifier that identifies the algorithm and algorithm-specific data, Java uses the generic format SubjectPublicKeyInfo (SPKI) defined by X.509/PKIX for public keys, which Java calls X509EncodedKeySpec, containing an AlgId plus algorithm-specific data. (See the javadoc for java.security.Key; for some reason I am currently unable to access docs.oracle.com to get a link.) You have only the algorithm-specific data defined by PKCS1 RSAPublicKey.

    You can parse and use it 'manually' with BouncyCastle, or convert it to SPKI and use that. Or (given BC or another ASN.1 library) you could use the same approach as in #31941413 except omit the Integer version (0) and wrap the data in a DERBitString instead of a DEROctetString, or the simpler and more direct approach I show in RSA should I use X.509 or PKCS #1 .

    Note this is not 'generic'. Your format is the opposite of algorithm-generic, which as noted is the purpose of SPKI and PCKS8. It is also not applciation-generic; among other things OpenSSH, PGP, Microsoft, PKCS11, JWK, and XML all use publickey formats different from this and not easily compatible with Java.