fail. Look but DO NOT TOUCH. if excess := len(b)*8 - c.N.BitLen(); excess > 0 { // Just to be safe, assert that this only happens for the one curve that // doesn't have a round number of bits. if c.curve != p521 { panic("ecdsa: internal error: unexpectedly masking off bits") } b = rightShift(b, excess) } // FIPS 186-5, Appendix A.4.2 makes us check x <= N - 2 and then return // x + 1. Note that it follows that 0 < x + 1 < N. Instead, SetBytes // checks that k < N, and we explicitly check 0 != k....