Brian, Here the theory:
If in X.509 certificate: Q_Uncompressed = 04 || Qx || Qy, Normally Q_Compressed = 02 || Qx if Qy is even, and = 03 || Qy if Qy is odd. And in C.509 certificate: 02 is replaced by 0xFE, and 03 by 0xFD. (Or just 0x0100 - first byte, since 02 + 0xFE = 0x0100 = 03 + 0xFD) Lijun > On 30. Jul 2024, at 23:43, Sipos, Brian J. <[email protected]> wrote: > > > For the second difference it appears to be a nuance related to the > compression defined in Section 3.2.1 of [1]. Is this conversion as simple as > translating the first octet between 0x02 or 0x03 to 0xFD or 0xFE > respectively? The c509 draft might be a little more explicit on this point > for those of us familiar with manipulating X509 structures opaquely but not > familiar with specific field encodings.
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