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Constructing an ECPublic Key in Java from Java Card

This question relates to this one here: Recovering an ECPublicKey from JavaCard to Java

However in the answer it isn't explained how to extract x and y - how can I do this?

Solution

  • The 'w' value is made up of the x and y values.

    The first byte should be either 04, 02 or 03 - which indicates if it is uncompressed or compressed. The last two bytes are status bytes, e.g. 90 00.

    The remaining bytes are the x, then y value, which are both the same length