What does Intel IPP status -220 (ippStsPointAtInfinity) mean?

 
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ippStsLoadDynErr ippStsI18nUnsupportedErr

ippStsPointAtInfinity

Why the infinity point is special

On an elliptic curve, the point at infinity is the identity element of the group. It is a valid internal result of point arithmetic, but it has no ordinary affine x and y coordinates. IPP therefore reports this status when an operation such as exporting coordinates or setting an SM2 key requires a finite point.

This is different from a point that is outside the field or not on the selected curve. Those conditions indicate malformed coordinates or a context mismatch; the infinity point can arise from otherwise valid arithmetic, for example when a scalar is congruent to zero modulo the subgroup order.

What to verify

  • Validate imported public points and perform the subgroup checks required by the protocol before using them.
  • Check whether a derived scalar was reduced to zero or whether two operands canceled each other.
  • Do not invent coordinates for infinity or serialize it as an all-zero public key unless the protocol explicitly defines such an encoding.
  • Keep this status distinct from ippStsOutOfRangeErr and from a curve-membership test that reports an invalid finite point.

References

Intel Cryptography Primitives: GFpECESSetKey_SM2 · Intel ipp-crypto status definitions · SEC 1: Elliptic Curve Cryptography


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