# RFC Errata

Found 7 records.

## Status: Verified (3)

#### RFC 7748, "Elliptic Curves for Security", January 2016

Source of RFC: IRTF
Errata ID: 4730

**Status: Verified
Type: Technical
Publication Format(s) : TEXT**

Reported By: Adam Langley

Date Reported: 2016-07-05

Verifier Name: Lars Eggert

Date Verified: 2016-07-05

Section 4.1 says:

V(P) 147816194475895447910205935684099868872646061346164752889648818 37755586237401

It should say:

V(P) 431144251710685529207648989359339670393703861982038067307639101 66200978582548

Notes:

The Montgomery form of the curve is generally used with a ladder, where the v coordinate is unused and unspecified. Thus I picked the smaller of the two possible values for v.

However, the curve is birationally equivalent to edwards25519, where both coordinates of the base point are used and are already in widespread use. Sadly, picking the smaller of the values for v ends up mapping to the negative of the base point on edwards25519.

This change replaces v with -v so that it matches up.

Errata ID: 7625

**Status: Verified
Type: Technical
Publication Format(s) : TEXT**

Reported By: Tomasz Mioduszewski

Date Reported: 2023-08-31

Verifier Name: Stanislav Smyshlyaev

Date Verified: 2023-09-04

Section 5 says:

swap ^= k_t

It should say:

swap = swap XOR k_t

Notes:

The '^' symbol is used inconsistently. In the line `swap ^= k_t` this symbol means the XOR operation, while later, e.g. in line `x_3 = (DA + CB)^2`, it indicates exponentiation. Pseudocode in this document also denotes the XOR operation in the following way: `x_2 = x_2 XOR dummy`. The inconsistent use of the '^' symbol may cause confusion. If one were to perform the operation `swap = swap (to the power of) k_t` instead of `swap = swap XOR k_t`, they would get incorrect results.

Errata ID: 5028

**Status: Verified
Type: Editorial
Publication Format(s) : TEXT**

Reported By: Adam Langley

Date Reported: 2017-06-02

Verifier Name: Stanislav Smyshlyaev

Date Verified: 2020-12-15

Section 5.2 says:

Input u-coordinate as a number (base 10):

It should say:

Decoded u-coordinate as a number (base 10):

Notes:

It is unclear that the base 10 numbers are the decoded values (i.e. after masking). That should have been made more explicit to reduce confusion.

## Status: Reported (2)

#### RFC 7748, "Elliptic Curves for Security", January 2016

Source of RFC: IRTF
Errata ID: 7096

**Status: Reported
Type: Technical
Publication Format(s) : TEXT**

Reported By: James Muir

Date Reported: 2022-08-18

Section Appendix A says:

# section A.1 sage code: for A in xrange(3, int(1e9)): if (A-2) % 4 != 0: continue # section A.3 sage code: for uInt in range(1, 1e3): u = F(uInt)

It should say:

# section A.1 sage code: for A in xsrange(3, int(1e9)): if (A-2) % 4 != 0: continue # section A.3 sage code: for uInt in xsrange(1, int(1e3)): u = F(uInt)

Notes:

"xrange" is not recognized by Sage with python 3, so the script from section A.1 fails with a syntax error (using "xrange" likely worked fine for Sage with python 2). The suggested changes in A.3 are just for consistency.

Errata ID: 7095

**Status: Reported
Type: Editorial
Publication Format(s) : TEXT**

Reported By: James Muir

Date Reported: 2022-08-18

Section Appendix A says:

This section specifies the procedure that was used to generate the above curves; specifically, it defines how to generate the parameter A of the Montgomery curve y^2 = x^3 + A*x^2 + x.

It should say:

This section specifies the procedure that was used to generate the above curves; specifically, it defines how to generate the parameter A of the Montgomery curve v^2 = u^3 + A*u^2 + u.

Notes:

For consistency with the other parts of the document (e.g. Section 3), use the variables u and v in the Montgomery curve equation.

## Status: Rejected (2)

#### RFC 7748, "Elliptic Curves for Security", January 2016

Source of RFC: IRTF
Errata ID: 5568

**Status: Rejected
Type: Technical
Publication Format(s) : TEXT**

Reported By: Juan Alcasabas

Date Reported: 2018-12-07

Rejected by: Stanislav Smyshlyaev

Date Rejected: 2020-12-15

Section 5.2 says:

Input u-coordinate: e5210f12786811d3f4b7959d0538ae2c31dbe7106fc03c3efc4cd549c715a493

It should say:

Input u-coordinate: e5210f12786811d3f4b7959d0538ae2c31dbe7106fc03c3efc4cd549c715a413

Notes:

In the X25519 2nd test vector the last byte of input u-coordinate should be 13 instead of 93. This will fix inconsistency between u-coordinate, its base10 representation and the output u-coordinate.

--VERIFIER NOTES--

A change of one bit of the input u-coordinate in the hexadecimal representation is proposed (to make it "consistent" with the base 10 representation). However, implementations of x25519 should "mask" that bit after taking a u-coordinate as an input - therefore, the existing text of RFC does not have any errors there.

Errata ID: 5651

**Status: Rejected
Type: Technical
Publication Format(s) : TEXT**

Reported By: Pierre Laurent

Date Reported: 2019-03-11

Rejected by: Stanislav Smyshlyaev

Date Rejected: 2020-12-15

Section 5 says:

z_2 = E * (AA + a24 * E)

It should say:

z_2 = E * (BB + a24 * E)

Notes:

When BB is used, the point multiplication of the second test vector

P = (0x13a415c749d54cfc3e3cc06f10e7db312cae38059d95b7f4d3116878120f21e5, 0x1)

by scalar k

0x4dba18799e16a42cd401eae021641bc1f56a7d959126d25a3c67b4d1d4e96648

gives the expected point

[k]P = (0x5779ac7a64f7f8e652a19f79685a598bf873b8b45ce4ad7a7d90e87694decb95, 0x1)

The implementation based on AA gives the unexpected point

[k]P = (0x3884d5c22af664f822cb3dd728b03c9fac1e1d78c772a74f05546566bd7bed9c, 1)

--VERIFIER NOTES--

It is proposed to modify the algorithm description for calculation of z_2. However, after checking the original algorithm independently, it was confirmed that the expected numbers are obtained. Therefore, the existing text of RFC does not have any errors here.