Re: [Curdle] draft-ietf-curdle-pkix and endianess of strings

[Jeffrey Walton <[e-mail]>]

On Wed, Dec 19, 2018 at 6:03 PM David Benjamin <[e-mail]> wrote:
> ...
> To that end, the quoted text talks about using curve parameters explicitly rather than a non-named curve. RFC 8410 doesn't specify such a thing. I would have made a lot of noise if it had. :-) Which encoding is this referring to?

Thanks David.

I have this test program handy for interop testing. I believe it is
using the EC key format from RFC 5480. This is what everyone has been
using in the void before the latest IETF deliverables.

In the program below the OID is new, but previous to getting Thawte's
OID we used GNU's old OID for curve25519. In between new (Thawte) and
old (GNU) we could use the OID's draft-josefsson-pkix-newcurves. Many
folks have to support 8 or 10 OIDs for the curves.

EC domain parameters (instead of a named curve) was going to be my
next test case to ensure we interop or work as expected.

I guess the point is, just because the latest RFC does not specify it,
it does not mean it is not going to happen. In fact, it has been
happening for years now because of the information void. RFC 5480
(with a mashup of OIDs) was enough to keep us going.

Jeff

$ cat x25519.c
#include <openssl/evp.h>
#include <openssl/pem.h>

int main (int argc, char* argv)
{
    EVP_PKEY *pkey = NULL;
    EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_X25519, NULL);
    EVP_PKEY_keygen_init(pctx);
    EVP_PKEY_keygen(pctx, &pkey);
    EVP_PKEY_CTX_free(pctx);
    PEM_write_PrivateKey(stdout, pkey, NULL, NULL, 0, NULL, NULL);
    return 0;
}

And then compile it. In the example below, OpenSSL was configured with
--prefix=/opt/openssl-1.1.1.

$ gcc -I /opt/openssl-1.1.1/include/ -L /opt/openssl-1.1.1/lib
x25519.c -o x25519.exe -l:libcrypto.a -lpthread -ldl$

And finally:

$ ./x25519.exe
-----BEGIN PRIVATE KEY-----
MC4CAQAwBQYDK2VuBCIEIMBio4/nGHPiJzCUDifuMl7zg6Me2XlI5jAKCyPRlW5R
-----END PRIVATE KEY-----

$ echo MC4CAQAwBQYDK2VuBCIEIMBio4/nGHPiJzCUDifuMl7zg6Me2XlI5jAKCyPRlW5R
| base64 -d > x25519.bin

$ dumpasn1 x25519.bin
  0  46: SEQUENCE {
  2   1:   INTEGER 0
  5   5:   SEQUENCE {
  7   3:     OBJECT IDENTIFIER curveX25519 (1 3 101 110)
       :     }
 12  34:   OCTET STRING, encapsulates {
 14  32:     OCTET STRING
       :       C0 62 A3 8F E7 18 73 E2 27 30 94 0E 27 EE 32 5E
       :       F3 83 A3 1E D9 79 48 E6 30 0A 0B 23 D1 95 6E 51
       :     }
       :   }

0 warnings, 0 errors.