在Java中加载原始的64字节长ECDSA公钥

private static byte[] P256_HEAD = Base64.getDecoder().decode("MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE");

public static ECPublicKey convertP256Key(byte[] w) throws InvalidKeySpecException {
    byte[] encodedKey = new byte[P256_HEAD.length + w.length];
    System.arraycopy(P256_HEAD,encodedKey,P256_HEAD.length);
    System.arraycopy(w,P256_HEAD.length,w.length);
    KeyFactory eckf;
    try {
        eckf = KeyFactory.getInstance("EC");
    } catch (NoSuchAlgorithmException e) {
        throw new IllegalStateException("EC key factory not present in runtime");
    }
    X509EncodedKeySpec ecpks = new X509EncodedKeySpec(encodedKey);
    return (ECPublicKey) eckf.generatePublic(ecpks);
}

用法：

ECPublicKey key = convertP256Key(w);
System.out.println(key);

我用头脑使用：

private static byte[] createHeadForNamedCurve(String name,int size)
        throws NoSuchAlgorithmException,InvalidAlgorithmParameterException,IOException {
    KeyPairGenerator kpg = KeyPairGenerator.getInstance("EC");
    ECGenParameterSpec m = new ECGenParameterSpec(name);
    kpg.initialize(m);
    KeyPair kp = kpg.generateKeyPair();
    byte[] encoded = kp.getPublic().getEncoded();
    return Arrays.copyOf(encoded,encoded.length - 2 * (size / Byte.SIZE));
}

来自：

String name = "NIST P-256";
int size = 256;
byte[] head = createHeadForNamedCurve(name,size);
System.out.println(Base64.getEncoder().encodeToString(head));

这样做的想法是创建一个X509编码的密钥,最终以公共点w结尾(包含命名曲线的OID的ASN.1 DER编码和结构开销的字节,以字节04结尾)表示未压缩点).然后我们用w替换最后的“随机”点w,然后再次解码.

Java 7需要EC 7功能和Java 8 for Base 64编码器/解码器,不需要额外的库和东西.请注意,打印时,实际上会将公钥显示为命名曲线,其他解决方案将不会执行.