node-forge-fromDer

1-demo.js

const forge = require("node-forge");

const badKeyValue = `MGsCAQEEIDrDtTbDnMKRwpvDpzkxLQpwO8O8w6zDq8OWwo
HCtcKedjrDgsOCMMOiw4rDqBsewpDCucKhRANCAAQ/c3zDq8K4wpnDvcO6N3nChsOUfnHD
k8OcQsORwqHCtMKFwrvCq08mw77CnsOHAl7DliQAwrsJX8OWYWzCn2lVw5DCg8OIeGfDpM
KxK8O4wr3Cn8OFdsO1HVhbw4xGWmbCpw==`;

const goodKeyValue = `MGsCAQEEIEjDv8KoIcO5wrrChl3DsUDDvXjDpMOYwrHDjMKKw
55pMT7CrMK8O8KQIsOTasK5SUZ7wqFEA0IABAQxUMOWennChGpcwoTDhsOvUzgeFsK3w7bCscK1wo
MDwrEuX8OPwrTCn8KUKcOiYcOtw6JRw7LDrSPCvMOtw4t/w4PDlcOQw5zDqiTCjDbCocKowpXCjMK
Uw41Vw49jE8Ogw7rDvEg=`;

const unBase64 = (s) => Buffer.from(s, "base64").toString();
const toHex = (s) => Buffer.from(s).toString("hex").slice(0, 15) + '...';

for (const [name, value] of [["bad", badKeyValue], ["good", goodKeyValue]]) {
  for (const decodeBitStrings of [true, false]) {
    const bytes = unBase64(value);
    const msg = forge.asn1.fromDer(bytes, { decodeBitStrings });
    const pvv = msg.value[2].value[0].value;

    console.log(name, "key, decode bit strings:", decodeBitStrings, "point value:",
      typeof pvv === "string" ? toHex(pvv) : `[{value: '${toHex(pvv[0].value)}'}]`,
      );
  }
}

2-output.txt

bad key, decode bit strings: true point value: [{value: '737cc3abc2b8c29...'}]
bad key, decode bit strings: false point value: 00043f737cc3abc...
good key, decode bit strings: true point value: 0004043150c3967...
good key, decode bit strings: false point value: 0004043150c3967...