# RFC Errata

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#### RFC 6090, "Fundamental Elliptic Curve Cryptography Algorithms", February 2011

Source of RFC: IETF - NON WORKING GROUP
Area Assignment: sec

Errata ID: 6329
Status: Reported
Type: Editorial
Publication Format(s) : TEXT

Reported By: Yannik Klubertanz
Date Reported: 2020-11-06

Section F.1. says:

```     if P is (@,@),
R = Q
else if Q is (@,@),
R = P
else if P is not equal to Q and x1 is equal to x2,
R = (@,@)
else if P is not equal to Q and x1 is not equal to x2,
x3 = ((y2-y1)/(x2-x1))^2 - x1 - x2 mod p and
y3 = (x1-x3)*(y2-y1)/(x2-x1) - y1 mod p
else if P is equal to Q and y1 is equal to 0,
R = (@,@)
else    // P is equal to Q and y1 is not equal to 0
x3 = ((3*x1^2 + a)/(2*y1))^2 - 2*x1 mod p and
y3 = (x1-x3)*(3*x1^2 + a)/(2*y1) - y mod p.

```

It should say:

```     if P is (@,@),
R = Q
else if Q is (@,@),
R = P
else if P is not equal to Q and x1 is equal to x2,
R = (@,@)
else if P is not equal to Q and x1 is not equal to x2,
x3 = ((y2-y1)/(x2-x1))^2 - x1 - x2 mod p and
y3 = (x1-x3)*(y2-y1)/(x2-x1) - y1 mod p
else if P is equal to Q and y1 is equal to 0,
R = (@,@)
else    // P is equal to Q and y1 is not equal to 0
x3 = ((3*x1^2 + a)/(2*y1))^2 - 2*x1 mod p and
y3 = (x1-x3)*(3*x1^2 + a)/(2*y1) - y1 mod p.

```

Notes:

In the last case in the pseudocode, there's a typo. It should be "y1" mod p instead of "y mod p".

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