Encoding of EC public keys?

[Tomas Gustavsson-3]

Hi,

I have a questions regarding encoding of EC public keys. I've come
across certificates (country signing certificates for ePassports) where
the public key is encoded with all parameters. When using BC only the
public point is encoded and an oid defines which curve is used.

Is there a correct way? I guess the oid way is newer and the other is an
old method?

Are both ways OK?

Kind regards,
Tomas

Full encoding:
-----
        Subject Public Key Info:
            Public Key Algorithm: id-ecPublicKey
            EC Public Key:
                pub:
                    04:97:9a:6e:87:ac:38:c4:93:02:73:a4:9d:07:86:
                    1e:aa:9a:d5:26:9d:a0:ac:62:7c:06:03:8a:34:49:
                    c0:52:2b:a3:db:4e:95:38:97:73:87:62:e5:ba:22:
                    73:3a:22:c9:fe:25:84:5c:78:c9:c1:cf:3e:61:67:
                    b6:49:60:86:00
                Field Type: prime-field
                Prime:
                    00:a9:fb:57:db:a1:ee:a9:bc:3e:66:0a:90:9d:83:
                    8d:72:6e:3b:f6:23:d5:26:20:28:20:13:48:1d:1f:
                    6e:53:77
                A:
                    7d:5a:09:75:fc:2c:30:57:ee:f6:75:30:41:7a:ff:
                    e7:fb:80:55:c1:26:dc:5c:6c:e9:4a:4b:44:f3:30:
                    b5:d9
                B:
                    26:dc:5c:6c:e9:4a:4b:44:f3:30:b5:d9:bb:d7:7c:
                    bf:95:84:16:29:5c:f7:e1:ce:6b:cc:dc:18:ff:8c:
                    07:b6
                Generator (uncompressed):
                    04:8b:d2:ae:b9:cb:7e:57:cb:2c:4b:48:2f:fc:81:
                    b7:af:b9:de:27:e1:e3:bd:23:c2:3a:44:53:bd:9a:
                    ce:32:62:54:7e:f8:35:c3:da:c4:fd:97:f8:46:1a:
                    14:61:1d:c9:c2:77:45:13:2d:ed:8e:54:5c:1d:54:
                    c7:2f:04:69:97
                Order:
                    00:a9:fb:57:db:a1:ee:a9:bc:3e:66:0a:90:9d:83:
                    8d:71:8c:39:7a:a3:b5:61:a6:f7:90:1e:0e:82:97:
                    48:56:a7
                Cofactor:  1 (0x1)
-----

BC encoding (it's not the same curve I know):
-----
        Subject Public Key Info:
            Public Key Algorithm: id-ecPublicKey
            EC Public Key:
                pub:
                    04:8b:97:62:79:fe:8e:a0:ec:b8:34:bd:27:91:63:
                    ef:92:8f:d7:6d:fd:89:74:cc:c7:16:24:bb:73:d1:
                    d4:eb:7b:f3:bd:bc:57:05:aa:c4:4b:19:8c:e6:f0:
                    b4:63:50:75:99:76:48:a4:54:69:d0:9f:01:5f:f1:
                    67:39:f7:e8:a7
                ASN1 OID: prime256v1
-----

[Tomas Gustavsson-3]

Hi,

some more clarifications. I have read up on some standards and realize
that IETF mandates the use of namedCurve while BSI-TR-03111 (icao)
mandates the use of ecParameters.

My problem is that ICAO mandates the 03111 way (ecParameters) for
country and document signing certificates used for ePassports.
Both ways seems ok according to standards.

How can I make BC produce certificate requests and certificates with
ecParameters instead of namedCurves?

Cheers,
Tomas

PS: I start to not like ecc due to the varying standards. You always
sooner or later end up in  "special handling" mode, which I don't like
as an implementor.

Tomas Gustavsson wrote:

> Hi,
>
> I have a questions regarding encoding of EC public keys. I've come
> across certificates (country signing certificates for ePassports) where
> the public key is encoded with all parameters. When using BC only the
> public point is encoded and an oid defines which curve is used.
>
> Is there a correct way? I guess the oid way is newer and the other is an
> old method?
>
> Are both ways OK?
>
> Kind regards,
> Tomas
>
> Full encoding:
> -----
>         Subject Public Key Info:
>             Public Key Algorithm: id-ecPublicKey
>             EC Public Key:
>                 pub:
>                     04:97:9a:6e:87:ac:38:c4:93:02:73:a4:9d:07:86:
>                     1e:aa:9a:d5:26:9d:a0:ac:62:7c:06:03:8a:34:49:
>                     c0:52:2b:a3:db:4e:95:38:97:73:87:62:e5:ba:22:
>                     73:3a:22:c9:fe:25:84:5c:78:c9:c1:cf:3e:61:67:
>                     b6:49:60:86:00
>                 Field Type: prime-field
>                 Prime:
>                     00:a9:fb:57:db:a1:ee:a9:bc:3e:66:0a:90:9d:83:
>                     8d:72:6e:3b:f6:23:d5:26:20:28:20:13:48:1d:1f:
>                     6e:53:77
>                 A:
>                     7d:5a:09:75:fc:2c:30:57:ee:f6:75:30:41:7a:ff:
>                     e7:fb:80:55:c1:26:dc:5c:6c:e9:4a:4b:44:f3:30:
>                     b5:d9
>                 B:
>                     26:dc:5c:6c:e9:4a:4b:44:f3:30:b5:d9:bb:d7:7c:
>                     bf:95:84:16:29:5c:f7:e1:ce:6b:cc:dc:18:ff:8c:
>                     07:b6
>                 Generator (uncompressed):
>                     04:8b:d2:ae:b9:cb:7e:57:cb:2c:4b:48:2f:fc:81:
>                     b7:af:b9:de:27:e1:e3:bd:23:c2:3a:44:53:bd:9a:
>                     ce:32:62:54:7e:f8:35:c3:da:c4:fd:97:f8:46:1a:
>                     14:61:1d:c9:c2:77:45:13:2d:ed:8e:54:5c:1d:54:
>                     c7:2f:04:69:97
>                 Order:
>                     00:a9:fb:57:db:a1:ee:a9:bc:3e:66:0a:90:9d:83:
>                     8d:71:8c:39:7a:a3:b5:61:a6:f7:90:1e:0e:82:97:
>                     48:56:a7
>                 Cofactor:  1 (0x1)
> -----
>
> BC encoding (it's not the same curve I know):
> -----
>         Subject Public Key Info:
>             Public Key Algorithm: id-ecPublicKey
>             EC Public Key:
>                 pub:
>                     04:8b:97:62:79:fe:8e:a0:ec:b8:34:bd:27:91:63:
>                     ef:92:8f:d7:6d:fd:89:74:cc:c7:16:24:bb:73:d1:
>                     d4:eb:7b:f3:bd:bc:57:05:aa:c4:4b:19:8c:e6:f0:
>                     b4:63:50:75:99:76:48:a4:54:69:d0:9f:01:5f:f1:
>                     67:39:f7:e8:a7
>                 ASN1 OID: prime256v1
> -----
>

[David Hook-2]

You can do this by either changing the way the KeyPairGenerator is
initialised or by rebuilding the public key by hand, replacing the
ECNamedCurveSpec with one that is just made up of the corresponding
parameters.

Regards,

David

PS. If you're dealing with parameters explicitly you might also need to
pay attention the implications of
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6738532


On Thu, 2009-10-29 at 13:31 +0100, Tomas Gustavsson wrote:

> Hi,
>
> some more clarifications. I have read up on some standards and realize
> that IETF mandates the use of namedCurve while BSI-TR-03111 (icao)
> mandates the use of ecParameters.
>
> My problem is that ICAO mandates the 03111 way (ecParameters) for
> country and document signing certificates used for ePassports.
> Both ways seems ok according to standards.
>
> How can I make BC produce certificate requests and certificates with
> ecParameters instead of namedCurves?
>
> Cheers,
> Tomas
>
> PS: I start to not like ecc due to the varying standards. You always
> sooner or later end up in  "special handling" mode, which I don't like
> as an implementor.
>
> Tomas Gustavsson wrote:
> > Hi,
> >
> > I have a questions regarding encoding of EC public keys. I've come
> > across certificates (country signing certificates for ePassports) where
> > the public key is encoded with all parameters. When using BC only the
> > public point is encoded and an oid defines which curve is used.
> >
> > Is there a correct way? I guess the oid way is newer and the other is an
> > old method?
> >
> > Are both ways OK?
> >
> > Kind regards,
> > Tomas
> >
> > Full encoding:
> > -----
> >         Subject Public Key Info:
> >             Public Key Algorithm: id-ecPublicKey
> >             EC Public Key:
> >                 pub:
> >                     04:97:9a:6e:87:ac:38:c4:93:02:73:a4:9d:07:86:
> >                     1e:aa:9a:d5:26:9d:a0:ac:62:7c:06:03:8a:34:49:
> >                     c0:52:2b:a3:db:4e:95:38:97:73:87:62:e5:ba:22:
> >                     73:3a:22:c9:fe:25:84:5c:78:c9:c1:cf:3e:61:67:
> >                     b6:49:60:86:00
> >                 Field Type: prime-field
> >                 Prime:
> >                     00:a9:fb:57:db:a1:ee:a9:bc:3e:66:0a:90:9d:83:
> >                     8d:72:6e:3b:f6:23:d5:26:20:28:20:13:48:1d:1f:
> >                     6e:53:77
> >                 A:
> >                     7d:5a:09:75:fc:2c:30:57:ee:f6:75:30:41:7a:ff:
> >                     e7:fb:80:55:c1:26:dc:5c:6c:e9:4a:4b:44:f3:30:
> >                     b5:d9
> >                 B:
> >                     26:dc:5c:6c:e9:4a:4b:44:f3:30:b5:d9:bb:d7:7c:
> >                     bf:95:84:16:29:5c:f7:e1:ce:6b:cc:dc:18:ff:8c:
> >                     07:b6
> >                 Generator (uncompressed):
> >                     04:8b:d2:ae:b9:cb:7e:57:cb:2c:4b:48:2f:fc:81:
> >                     b7:af:b9:de:27:e1:e3:bd:23:c2:3a:44:53:bd:9a:
> >                     ce:32:62:54:7e:f8:35:c3:da:c4:fd:97:f8:46:1a:
> >                     14:61:1d:c9:c2:77:45:13:2d:ed:8e:54:5c:1d:54:
> >                     c7:2f:04:69:97
> >                 Order:
> >                     00:a9:fb:57:db:a1:ee:a9:bc:3e:66:0a:90:9d:83:
> >                     8d:71:8c:39:7a:a3:b5:61:a6:f7:90:1e:0e:82:97:
> >                     48:56:a7
> >                 Cofactor:  1 (0x1)
> > -----
> >
> > BC encoding (it's not the same curve I know):
> > -----
> >         Subject Public Key Info:
> >             Public Key Algorithm: id-ecPublicKey
> >             EC Public Key:
> >                 pub:
> >                     04:8b:97:62:79:fe:8e:a0:ec:b8:34:bd:27:91:63:
> >                     ef:92:8f:d7:6d:fd:89:74:cc:c7:16:24:bb:73:d1:
> >                     d4:eb:7b:f3:bd:bc:57:05:aa:c4:4b:19:8c:e6:f0:
> >                     b4:63:50:75:99:76:48:a4:54:69:d0:9f:01:5f:f1:
> >                     67:39:f7:e8:a7
> >                 ASN1 OID: prime256v1
> > -----
> >
>