Example usage for org.bouncycastle.asn1.sec ECPrivateKey getParameters

Introduction

In this page you can find the example usage for org.bouncycastle.asn1.sec ECPrivateKey getParameters.

Prototype

public ASN1Primitive getParameters() 

Source Link

Usage

From source file:edu.tamu.tcat.crypto.bouncycastle.ASN1SeqKeyImpl.java

License:Apache License

private static PrivateKey decodeECKey(byte[] encodedKey) throws EncodingException {
    try {/*from   ww w.  jav  a2 s  . com*/
        ECPrivateKey priv = ECPrivateKey.getInstance(encodedKey);
        ASN1Sequence parameters = (ASN1Sequence) priv.getParameters();

        ASN1Integer version = (ASN1Integer) parameters.getObjectAt(0);
        if (version.getPositiveValue().intValue() != 1)
            throw new EncodingException("Only know how to decode version 1");
        ASN1Sequence fieldId = (ASN1Sequence) parameters.getObjectAt(1);
        ASN1Encodable fieldType = fieldId.getObjectAt(0);
        ECField field;
        if (fieldType.toString().equals("1.2.840.10045.1.1")) {
            ASN1Integer primeObject = (ASN1Integer) fieldId.getObjectAt(1);
            field = new ECFieldFp(primeObject.getPositiveValue());
        } else
            throw new EncodingException("Only know how to decode prime fields");
        ASN1Sequence curveSeq = (ASN1Sequence) parameters.getObjectAt(2);

        ASN1OctetString a = (ASN1OctetString) curveSeq.getObjectAt(0);
        ASN1OctetString b = (ASN1OctetString) curveSeq.getObjectAt(1);
        EllipticCurve curve;
        if (curveSeq.size() > 2) {
            DERBitString seed = (DERBitString) curveSeq.getObjectAt(2);
            curve = new EllipticCurve(field, getInteger(a.getOctets()), getInteger(b.getOctets()),
                    seed.getBytes());
        } else
            curve = new EllipticCurve(field, getInteger(a.getOctets()), getInteger(b.getOctets()));

        ASN1OctetString gEncoded = (ASN1OctetString) parameters.getObjectAt(3);
        ECPoint g = ECPointUtil.decodePoint(curve, gEncoded.getOctets());
        ASN1Integer n = (ASN1Integer) parameters.getObjectAt(4);
        ASN1Integer h = (ASN1Integer) parameters.getObjectAt(5);
        ECParameterSpec paramSpec = new ECParameterSpec(curve, g, n.getPositiveValue(),
                h.getPositiveValue().intValue());

        ECPrivateKeySpec spec = new ECPrivateKeySpec(priv.getKey(), paramSpec);
        KeyFactory factory = KeyFactory.getInstance("EC", Activator.getDefault().getBouncyCastleProvider());
        PrivateKey key = factory.generatePrivate(spec);
        return key;
    } catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
        throw new EncodingException("Failed decoding type [EC]", e);
    }
}

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