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For example, with openssl I have seen that facebook works with ANSI X9.62 prime256v1 elliptic curve and what I want is the point of the curve that is using with my signature. I have seen that I can extract the point from facebook certificate, in the public key.

So again with openssl I get the public key:

-----BEGIN PUBLIC KEY-----
MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEoPGMr6c5iGhbE1YOFRW0p0XvG8fl
hTwrBNRlijExIuqjku1knbplgeO2EnbYswtF8f8KKBScT9xzqbNJLaB20w==
-----END PUBLIC KEY-----

But now I don't know how to get it. Anyone knows how to do it? Or am I doing it wrong? I can do operations with Sage.

Thanks

1

Not sure, but is this what you are looking for?

$ cat pubkey.pub
-----BEGIN PUBLIC KEY-----
MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEoPGMr6c5iGhbE1YOFRW0p0XvG8fl
hTwrBNRlijExIuqjku1knbplgeO2EnbYswtF8f8KKBScT9xzqbNJLaB20w==
-----END PUBLIC KEY-----

$ openssl ec -pubin -in pubkey.pub -noout -text
read EC key
Private-Key: (256 bit)
pub:
    04:a0:f1:8c:af:a7:39:88:68:5b:13:56:0e:15:15:
    b4:a7:45:ef:1b:c7:e5:85:3c:2b:04:d4:65:8a:31:
    31:22:ea:a3:92:ed:64:9d:ba:65:81:e3:b6:12:76:
    d8:b3:0b:45:f1:ff:0a:28:14:9c:4f:dc:73:a9:b3:
    49:2d:a0:76:d3
ASN1 OID: prime256v1
NIST CURVE: P-256

$ openssl ec -pubin -in pubkey.pub -noout -text -param_enc explicit
read EC key
Private-Key: (256 bit)
pub:
    04:a0:f1:8c:af:a7:39:88:68:5b:13:56:0e:15:15:
    b4:a7:45:ef:1b:c7:e5:85:3c:2b:04:d4:65:8a:31:
    31:22:ea:a3:92:ed:64:9d:ba:65:81:e3:b6:12:76:
    d8:b3:0b:45:f1:ff:0a:28:14:9c:4f:dc:73:a9:b3:
    49:2d:a0:76:d3
Field Type: prime-field
Prime:
    00:ff:ff:ff:ff:00:00:00:01:00:00:00:00:00:00:
    00:00:00:00:00:00:ff:ff:ff:ff:ff:ff:ff:ff:ff:
    ff:ff:ff
A:
    00:ff:ff:ff:ff:00:00:00:01:00:00:00:00:00:00:
    00:00:00:00:00:00:ff:ff:ff:ff:ff:ff:ff:ff:ff:
    ff:ff:fc
B:
    5a:c6:35:d8:aa:3a:93:e7:b3:eb:bd:55:76:98:86:
    bc:65:1d:06:b0:cc:53:b0:f6:3b:ce:3c:3e:27:d2:
    60:4b
Generator (uncompressed):
    04:6b:17:d1:f2:e1:2c:42:47:f8:bc:e6:e5:63:a4:
    40:f2:77:03:7d:81:2d:eb:33:a0:f4:a1:39:45:d8:
    98:c2:96:4f:e3:42:e2:fe:1a:7f:9b:8e:e7:eb:4a:
    7c:0f:9e:16:2b:ce:33:57:6b:31:5e:ce:cb:b6:40:
    68:37:bf:51:f5
Order:
    00:ff:ff:ff:ff:00:00:00:00:ff:ff:ff:ff:ff:ff:
    ff:ff:bc:e6:fa:ad:a7:17:9e:84:f3:b9:ca:c2:fc:
    63:25:51
Cofactor:  1 (0x1)
Seed:
    c4:9d:36:08:86:e7:04:93:6a:66:78:e1:13:9d:26:
    b7:81:9f:7e:90

$ openssl asn1parse -in pubkey.pub -i -dump
    0:d=0  hl=2 l=  89 cons: SEQUENCE
    2:d=1  hl=2 l=  19 cons:  SEQUENCE
    4:d=2  hl=2 l=   7 prim:   OBJECT            :id-ecPublicKey
   13:d=2  hl=2 l=   8 prim:   OBJECT            :prime256v1
   23:d=1  hl=2 l=  66 prim:  BIT STRING
      0000 - 00 04 a0 f1 8c af a7 39-88 68 5b 13 56 0e 15 15   .......9.h[.V...
      0010 - b4 a7 45 ef 1b c7 e5 85-3c 2b 04 d4 65 8a 31 31   ..E.....<+..e.11
      0020 - 22 ea a3 92 ed 64 9d ba-65 81 e3 b6 12 76 d8 b3   "....d..e....v..
      0030 - 0b 45 f1 ff 0a 28 14 9c-4f dc 73 a9 b3 49 2d a0   .E...(..O.s..I-.
      0040 - 76 d3                                             v.

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