Parsing ECC public / private key in Java (generated by GPG CLI)

I am trying to convert the ECC GPG key of armor to the corresponding Java class

To generate the key pair I am using: GPG – expert – full generate key

Then select (9) ECC and ECC (or (10) ECC (signature only))

Then select (3) NIST p-256

Result in:

-----BEGIN PGP PUBLIC KEY BLOCK-----

mFIEWUdzwhMIKoZIzj0DAQcCAwQkAvZC1PIJ8ke1myyKhNny9vN78TIYo2MuAOY+
F38L9S3+Za9cKV/iIHOqfapbMoqdSmSnqDkevwQSr5MF2UOXtCJzaWduZWNjIChF
Q0Mgc2lnbiBvbmx5KSA8c3NAc3MuY28+iJAEExMIADgWIQRiC+kefVkjnjKovKy5
XANFl5+n1gUCWUdzwgIbAwULCQgHAgYVCAkKCwIEFgIDAQIeAQIXgAAKCRC5XANF
l5+n1mzGAQDsgutymxDTTXPKFfpFFVp4fxacx1MSqxP71gNJYjguXwD8CEXD20Vm
aU1WMi2jU7JC6oJn94Y4vWHwTLOU1zmQ19o=
=swfS
-----END PGP PUBLIC KEY BLOCK-----

-----BEGIN PGP PRIVATE KEY BLOCK-----

lHcEWUdzwhMIKoZIzj0DAQcCAwQkAvZC1PIJ8ke1myyKhNny9vN78TIYo2MuAOY+
F38L9S3+Za9cKV/iIHOqfapbMoqdSmSnqDkevwQSr5MF2UOXAAD9FhS2HZoWOyIi
l9nj+WPa9S1o50jM5bNIRALzcyS8SgoP97Qic2lnbmVjYyAoRUNDIHNpZ24gb25s
eSkgPHNzQHNzLmNvPoiQBBMTCAA4FiEEYgvpHn1ZI54yqLysuVwDRZefp9YFAllH
c8ICGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQuVwDRZefp9ZsxgEA7ILr
cpsQ001zyhX6RRVaeH8WnMdTEqsT+9YDSWI4Ll8A/AhFw9tFZmlNVjIto1OyQuqC
Z/eGOL1h8EyzlNc5kNfa
=qHBB
-----END PGP PRIVATE KEY BLOCK-----

How to get valid Java. XML from this armored text format security. interfaces. Ecprivatekey and Java security. interfaces. Ecpublickey Java class?

My ultimate goal is to sign in the following ways:

String createSignatureFromJson(String jsonPayload,byte[] privateKey) {
        Payload payload = new Payload(jsonPayload)
        def key = privateKeyParse(privateKey)

        JWSSigner signer = new ECDSASigner((ECPrivateKey)key)
        JWSHeader header = new JWSHeader.Builder(JWSAlgorithm.ES256).build()

        JWSObject jwsObject = new JWSObject(header,payload)
        jwsObject.sign(signer)
        jwsObject.signature
    }

Solution

If you just pass the 'private key block', this will extract the ecprivatekey:

private static ECPrivateKey privateKeyParse(byte[] privateKey) throws Exception
{
    InputStream pgpIn = PGPUtil.getDecoderStream(new ByteArrayInputStream(privateKey));

    PGPObjectFactory pgpFact = new PGPObjectFactory(pgpIn,new JcaKeyFingerprintCalculator());
    PGPSecretKeyRing pgpSecRing = (PGPSecretKeyRing)pgpFact.nextObject();
    PGPSecretKey pgpSec = pgpSecRing.getSecretKey();
    PGPPrivateKey pgpPriv = pgpSec.extractPrivateKey(null);

    return (ECPrivateKey)new JcaPGPKeyConverter().getPrivateKey(pgpPriv);
}

To answer the comment on how to get 'privatekey', if the whole:

-----BEGIN PGP PRIVATE KEY BLOCK-----
...
-----END PGP PRIVATE KEY BLOCK-----

In a file, and then just read the whole file into a byte []:

InputStream fIn = new BufferedInputStream(new FileInputStream(...));
byte[] privateKey = org.bouncycastle.util.io.Streams.readAll(fIn);