Take the 2-minute tour ×
Cryptography Stack Exchange is a question and answer site for software developers, mathematicians and others interested in cryptography. It's 100% free, no registration required.

In projective coordinates point-at-infinity can be identified with z=0. How to identify the point-at-infinity in affine coordinate.

Whether x=0 and y=0 can be considered as point-at-infinity in affine coordinate?

share|improve this question
1  
Does crypto.stackexchange.com/questions/6156/… help, by any chance? –  Thomas Feb 25 '13 at 5:58
    
@Thomas: I went through the link you posted. My question is not related to encoding of the point-at-infinity. In our implementation after EC operation such as EC point addition we return the point "x=0, y=0" when we encounter point-at-infinity. So I wanted to check is it safe in doing this? Is there a remote possibility of obtaining a valid point with x=0,y=0 when working with standard EC curves? –  Andy Feb 26 '13 at 4:15
    
Well, clearly (0,0) is a valid point for the curve y^2=x^3+x which is in the standard reduced Weierstrass form. If you want a simple encoding that can be unambiguous, why not use (p,0) where p is the cardinality of the field of definition ? –  minar Jul 3 '13 at 22:27
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.