Call to EC_POINT_set_compressed_coodinates() with with x-coordinate and
y-bit will resolve the curve equation for y and chooses y out of two
possible y values based on y-bit input.
You can retrieve the x and y co-ordinates using
EC_POINT_get_affine_coordinates as below, where x-cordinate matches w
I checked the 'test' folder but I didn't found any tests that help me
in this case.
However the only doubt is how I can use the API offered by openssl library.
I understand how retreive a point (and consequently to assign it to a
public key) starting from a compressed-y representation (which
> If I have an x-point which follows this representation
> https://tools.ietf.org/id/draft-jivsov-ecc-compact-05.html (so it is
> composed by 33 byte and first byte is '0x02') and I use
> 'EC_POINT_set_compressed_coordinates_GFp' function, it will be
> considered as compressed-y-0 or compressed-y-1
But the y bit is indicated by the foutth parameter of
'EC_POINT_set_compressed_coordinates_GFp' function.
Isn't the representation you linked different by that that I linked
previously?
Luca
Thulasi Goriparthi ha scritto:
02 indicates y bit is 0
03 indicates y bit is 1
http://citeseerx.i
02 indicates y bit is 0
03 indicates y bit is 1
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.202.2977&rep=rep1&type=pdf
Thanks,
Thulasi.
On Fri, 25 Oct 2019 at 16:50, Luca Di Mauro wrote:
>
> Mh, maybe I didn't understand.
>
> If I have an x-point which follows this representation
Mh, maybe I didn't understand.
If I have an x-point which follows this representation
https://tools.ietf.org/id/draft-jivsov-ecc-compact-05.html (so it is
composed by 33 byte and first byte is '0x02') and I use
'EC_POINT_set_compressed_coordinates_GFp' function, it will be
considered as
> Thank you! I thought they were the same.
>
> And given an x-only coordinate, how can I find the y coordinate? I
> don't find the relative functions on the documentation.
Well it depends on what you mean. Internally,
EC_POINT_set_compressed_coordinates_GFp will internally automatically
compute th
Thank you! I thought they were the same.
And given an x-only coordinate, how can I find the y coordinate? I
don't find the relative functions on the documentation.
Luca
Billy Brumley ha scritto:
Don't do that. As I said, the library is trying to tell you that's not a
point on the secp256k
Don't do that. As I said, the library is trying to tell you that's not a
point on the secp256k1 curve.
Quickly browsing the standard, you are likely looking for the prime256v1
curve.
BBB
On Fri, 25 Oct 2019, 9.28 Luca Di Mauro, wrote:
> I think it is correct because I extracted the hexadecimal
I think it is correct because I extracted the hexadecimal string from
a packet contained in a pcap.
This compressed point is created following the ETSI TS 103 097 v1.3.1
standard for secured communications in the vehicular communication
context
(https://www.etsi.org/deliver/etsi_ts/103000
> EC_GROUP* group = EC_GROUP_new_by_curve_name (NID_secp256k1);
> "c16b4ce0532f5dc9d09114fe121d3956ae84f9eb677a0d4bdac1d3af7a91950c";
I don't believe there's a point on secp256k1 with that x-coordinate.
If you check the failure reason for
EC_POINT_set_compressed_coordinates_GFp in
Hi,
the link you posted below are very useful!
However, after many trials and errors, I created a little program to
derive a public key from an x-only coordinate but, in the last step,
it fails, namely in the function
'EC_POINT_set_compressed_coordinates_GFp' called in the function
'loadK
Thank you very much for the reply!
Yes, I have also the additional information about on which of two
solutions I should take.
I'll check the guides you linked below.
Luca Di Mauro
Nicola Tuveri ha scritto:
Hi,
with traditional EC from the x coordinate alone you can't really do that,
beca
Hi,
with traditional EC from the x coordinate alone you can't really do that,
because there are always 2 possible solutions for y (in R the curve is
symmetrical on the x axis).
The standards define a "compressed point" format in which you can send the
coordinate x and an additional bit to select
Hello all,
I don't know if it is the correct mailing list to ask this, so I'm
sorry if it is the wrong palce.
I'm using openssl v1.1, and I'm trying to compute both the X and Y
coordinates of an elliptic curve point starting from a single
coordinate (X or Y).
How can i perform that in
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