How to create ECPoint from raw private key

Question

How to create a bouncy castle ECPoint from a raw private key hex string? I am getting a private key using the 'dumpprivkey' RPC and removing the header byte and the 4 bytes of checksum + 1 byte of discriminator trailer bytes, resulting in a 32 byte raw key LIKE this example (this sample comes from here). It causes the following exception. Decoding public keys this way does not have this problem.

This is the code:

public static void main(String[] args) {
    String priv_key = "E9873D79C6D87DC0FB6A5778633389F4453213303DA61F20BD67FC233AA33262"; 
    BigInteger value = new BigInteger(priv_key, 16);
    ECCurve BITCOIN_CURVE = new SecP256K1Curve();
    ECPoint point = BITCOIN_CURVE.decodePoint(value.toByteArray());
}

But it results in this exception:

Exception in thread "main" java.lang.IllegalArgumentException: Incorrect length for infinity encoding
    at org.bouncycastle.math.ec.ECCurve.decodePoint(Unknown Source)
    at Btc.main(Btc.java:19)

Answer 1

A raw private key is not on the elliptic curve, so there will be no ECPoint. It is a random number as described here.