RFC 5903, "Elliptic Curve Groups modulo a Prime (ECP Groups) for IKE and IKEv2", June 2010Source of RFC: IETF - NON WORKING GROUP
Area Assignment: sec
Errata ID: 2308
Publication Format(s) : TEXT
Reported By: Alfred Hoenes
Date Reported: 2010-06-22
Rejected by: Sean Turner
Date Rejected: 2011-11-12
Section 3.1 - 3.3 says:
a) in Section 3.1: Field Size: 256 b) in Section 3.2: Field Size: 384 c) in Section 3.3: Field Size: 521
It should say:
a) Field bit width: 256 b) Field bit width: 384 c) Field bit width: 521
The "size" of a finite field is the number of elements of the field,
according to century-old well-established mathematical terminology.
In the case of Sections 3.1 through 3.3, the field width is the prime
number p given 3 lines above the given snippets.
The idea is to give the number of bits needed to represent the field
elements (integers modulo p), which serve as the x and y coordinates
of the Elliptic Curve group points -- hence this should be denoted as
the bit width of the field (elements), which equals ceil(lb(p)).
I just can't see keeping this as-is is going to cause any issues for implementers.