Re: [pkix] Question about Curve P-192
Dan Brown <danibrown@blackberry.com> Thu, 10 May 2018 18:51 UTC
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From: Dan Brown <danibrown@blackberry.com>
To: Russ Housley <housley@vigilsec.com>, Ernst G Giessmann <giessman@informatik.hu-berlin.de>
CC: IETF PKIX <pkix@ietf.org>
Thread-Topic: [pkix] Question about Curve P-192
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Date: Thu, 10 May 2018 18:51:00 +0000
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Subject: Re: [pkix] Question about Curve P-192
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Hi Denis, Please, do not use P-192, unless there are some severe constraints. Even if you credit EC with a very generous 16 extra bits in security (compared to hashes & ciphers), P-192 would only reach 96+16=112-bit security, which does not meet the current best practice of 128 bit security. History as I understand it: NIST P-192 was meant for the 80-bit level (though it looks like 96-bit). This low security level has been widely deprecated since 2010, at least informally - to what extent it is formally deprecated, I don't recall off-hand. I recall added text to ANSI X9.62/63 deprecating this security level. Anyway, originally, the idea was to use P-192 with SHA-1, P-224 with SHA-224, etc. I think that there were also OIDs for P-192, e.g. secp192k1, and OIDs for ECDSA-with-SHA1, which could be combined in some ways. I do not recall how far these OIDs made into IETF, i.e. as algorithm identifiers. Using 160-bit hash in ECDSA with P-192 renders the EU-CMA security to 80 bits, which is waste considering that P-192 potentially provides 96-bit security. As noted in the thread below, the standards have options to truncate a longer hash, which should correct this. Arguably, the security of P-192 has fared far better than SHA-1 in some ways, yet SHA-1 is probably much more widely used than P-192, though admittedly hashes are considered a general purpose tool. Best regards, Dan From: pkix [mailto:pkix-bounces@ietf.org] On Behalf Of Russ Housley Sent: Thursday, May 10, 2018 1:30 PM To: Ernst G Giessmann <giessman@informatik.hu-berlin.de> Cc: IETF PKIX <pkix@ietf.org> Subject: Re: [pkix] Question about Curve P-192 Ernst: Of course, this technique works. That said, I am not aware of any algorithm identifiers that make use of the P-192 curve for digital signature or key agreement. Russ On May 10, 2018, at 1:24 PM, Ernst G Giessmann <giessman@informatik.hu-berlin.de <mailto:giessman@informatik.hu-berlin.de> > wrote: Yes, there is a standardized way: Pick up a corresponding hash function, in case of P-192 it should be SHA-224 and take the 192 left most bits of the hash value as the input to the EC sign primitive. The correspondig signature suite can be defined with ISO 14888-3, which allows the specification of the algo (e.g. EC-DSA, EC-KCDSA or whatsoever), the curve and the hash function. Kind regards, /Ernst. Am 2018-05-10 um 19:07 schrieb Denis: Hello everybody, Curve P-192 is specified in FIPS PUB 186-4 (Digital Signature Standard (DSS)). There is no "SHA-192" hash function defined in FIPS PUB 180-4 (Secure Hash Standard (SHS)). Is there any standardized way to use a hash function with Curve P-192 ? Is there any RFC or any another document that specifies a cryptographic suite for Curve P-192 ? Denis _______________________________________________ pkix mailing list pkix@ietf.org <mailto:pkix@ietf.org> https://www.ietf.org/mailman/listinfo/pkix _______________________________________________ pkix mailing list pkix@ietf.org <mailto:pkix@ietf.org> https://www.ietf.org/mailman/listinfo/pkix
- [pkix] Question about Curve P-192 Denis
- Re: [pkix] Question about Curve P-192 Ernst G Giessmann
- Re: [pkix] Question about Curve P-192 Russ Housley
- Re: [pkix] Question about Curve P-192 Dan Brown
- Re: [pkix] Question about Curve P-192 Denis
- Re: [pkix] Question about Curve P-192 Michael StJohns
- Re: [pkix] Question about Curve P-192 Denis
- Re: [pkix] Question about Curve P-192 Dan Brown
- Re: [pkix] Question about Curve P-192 Denis
- Re: [pkix] Question about Curve P-192 Dan Brown
- Re: [pkix] Question about Curve P-192 Ernst G Giessmann
- Re: [pkix] Question about Curve P-192 Michael StJohns
- Re: [pkix] Question about Curve P-192 Ernst G Giessmann