Network Working Group D. Linsenbardt

Network Working Group D. Linsenbardt
Request for Comments: 4059 S. Pontius
Category: Informational A. Sturgeon
SPYRUS
May 2005

Internet X.509 Public Key Infrastructure
Warranty Certificate Extension

Status of This Memo

This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2005).

Abstract

This document describes a certificate extension to explicitly state
the warranty offered by a Certificate Authority (CA) for the
certificate containing the extension.

1. Introduction

The warranty certificate extension identifies the warranty policy
associated with a X.509 public key certificate [X.509-97, PROFILE].
Often the Certificate Authority (CA) will obtain an insurance policy
to ensure coverage of the warranty.

The certificate warranty provides an extended monetary coverage for
the end entities. The certificate warranty primarily concerns the
use, storage, and reliance on a certificate by a subscriber, a
relying party, and the CA. It is common for a CA to establish
reliance limits on the use of a certificate. It is not uncommon for
a CA to attempt through contractual means to exclude its liability
entirely. However, this undermines the confidence that commerce
requires to gainfully use certificates.

Alternatively a CA may provide extended coverage for the use of the
certificate. Usually, the subscriber pays for the extended warranty
coverage. In turn, subscribers are covered by an appropriately
drafted insurance policy. The certificate warranty is backed by an
insurance policy issued by a licensed insurance company, which
results in a financial backing that is far greater than that of the

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RFC 4059 Warranty Certificate Extension May 2005

CA. This extra financial backing provides a further element of
confidence necessary to encourage the use of certificates in
commerce.

A relying party that has a warranty from a CA may obtain compensation
from a CA depending on the conditions for such compensation expressed
in either the CA's Certificate Policy, the CA's insurance policy, or
both. Evidence of an extended warranty, provided through the
certificate extension, will give the relying party additional
confidence that compensation is possible, and therefore will enhance
trust in the process. Risk for a non-subscriber relying party may be
reduced by the presence of a warranty extension with an explicit
warranty stated. The warranty extension allows this aspect of risk
management to be automated.

When a certificate contains a warranty certificate extension, the
extension MUST be non-critical, and MUST contain either a NULL to
indicate that no warranty is provided or base warranty data to
indicate that a warranty is provided. The extension MAY contain
optional qualifiers.

1.1. Conventions Used in This Document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].

2. Warranty Extension Format

Like all X.509 certificate extensions, the warranty certificate
extension is defined using ASN.1 [X.208-88, X.209-88].

The non-critical warranty extension is identified by id-pe-warranty.

PKIX Object Identifier Registry
id-pkix OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
dod(6) internet(1) security(5) mechanisms(5) pkix(7) }

PKIX Arcs
id-mod OBJECT IDENTIFIER ::= { id-pkix 0 } -- modules
id-pe OBJECT IDENTIFIER ::= { id-pkix 1 } -- private
certificate extensions

PKIX modules
id-mod-warranty-extn OBJECT IDENTIFIER ::= { id-mod 27 }

id-pe-warranty OBJECT IDENTIFIER ::= { id-pe 16 }

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A non-null warranty always includes a base warranty. The warranty
information includes the period during which the warranty applies, a
warranty value, and a warranty type. The warranty type tells the
warranty limit against claims. The extension definition supports two
alternatives: aggregated and per-transaction. With aggregation,
claims are fulfilled until a ceiling value is reached. After that,
no further claims are fulfilled. With per-transaction, a ceiling
value is imposed on each claim, but each transaction is considered
independently.

The warranty extension permits inclusion of two optional warranty
qualifiers. The first qualifier provides extended warranty
information, the second provides a pointer to the warranty terms and
conditions.

When present, the extended warranty information provides information
about coverage beyond the scope of the base warranty. Like the base
warranty information, the extended warranty information includes the
period during which the warranty applies, a warranty value, and a
warranty type.

When present, the terms and conditions pointer provides a reference
to a document containing the terms and conditions associated with the
warranty. The document may be a Certificate Policy that contains
this information, a document specifically about the warranty, or a
Relying Party Agreement. The pointer is always a uniform resource
locator (URL). The URL MUST be a non-relative URL using the http
scheme. The URL MUST follow the URL syntax and encoding rules
specified in RFC 3986 [URI].

2.1. Warranty Extension Syntax

The syntax for the warranty extension is:

Warranty ::= CHOICE {
none NULL, -- No warranty provided
wData WarrantyData } -- Explicit warranty

WarrantyData ::= SEQUENCE {
base WarrantyInfo,
extended WarrantyInfo OPTIONAL,
tcURL TermsAndConditionsURL OPTIONAL }

WarrantyInfo ::= SEQUENCE {
validity WarrantyValidityPeriod,
amount CurrencyAmount,
wType WarrantyType }

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WarrantyValidityPeriod ::= CHOICE {
sameAsCertificate NULL,
explicitPeriod ValidityPeriod }

ValidityPeriod ::= SEQUENCE {
notBefore GeneralizedTime,
notAfter GeneralizedTime }

-- CurrencyAmount specifies the currency and a monetary value.
-- Currency codes are defined in [ISO4217]. The monetary value
-- is: amount / (10 ** amtExp10), and the exponent MUST be the
-- minor unit of currency specified in [ISO4217].

CurrencyAmount ::= SEQUENCE {
currency INTEGER (1..999),
amount INTEGER (0..MAX),
amtExp10 INTEGER (0..MAX) }

WarrantyType ::= INTEGER {
aggregated (0),
perTransaction (1) }

TermsAndConditionsURL ::= IA5String -- MUST use http scheme

2.2. Warranty Extension Semantics

Warranty is a CHOICE; it is represented either by NULL or
WarrantyData. If the CA selects NULL, then the CA is explicitly
stating that no warranty is provided. If the CA selects
WarrantyData, then the CA is explicitly stating that a warranty is
provided, and the fields within the WarrantyData type MUST provide
details about that warranty.

WarrantyData MUST contain information about the base warranty.
WarrantyData MAY contain information about an extended warranty.
Both base warranty and extended warranty information is provided
using the WarrantyInfo type. WarrantyData MAY contain a URL that
points to the terms and conditions of the warranty. The URL is
provided using the TermsAndConditionsURL type, which is an IA5
string. The IA5String MUST contain a URI [URI] using the http
scheme, such as "http://www.example.com/warranty/t_and_c.html".

WarrantyInfo MUST contain the warranty validity period, the currency
amount of the warranty, and the type of warranty. The warranty
validity period is provided using the WarrantyValidityPeriod type.
The currency amount of the warranty is provided using the
CurrencyAmount type. The type of warranty is provided using the
WarrantyType type.

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WarrantyValidityPeriod is a CHOICE; it is represented either by NULL
or ValidityPeriod. If the CA selects NULL, then the validity periods
of the warranty and the certificate MUST be exactly the same. If the
CA selects ValidityPeriod, then the CA is explicitly stating a
warranty validity period that is different than the validity period
of the certificate. If the validity periods of the warranty and the
certificate are the same, then the CA MUST select the NULL choice.
The validity periods are expected to be the same in the vast majority
of the cases. ValidityPeriod is a SEQUENCE of two GeneralizedTime
values. The first (notBefore) GeneralizedTime value MUST indicate
the date and time that the warranty becomes valid, and the second
(notAfter) GeneralizedTime value MUST indicate the date and time that
the warranty expires.

CurrencyAmount is a SEQUENCE of three integers which together specify
the currency and a monetary value. The first integer (currency) MUST
indicate the currency using one of the currency codes defined in
[ISO4217]. The second integer (amount) MUST indicate the value of
the warranty. The third integer (amtExp10) MUST indicate the correct
placement of the decimal point in the monetary value, and MUST be the
minor unit of currency specified in [ISO4217]. For example
$48,525.50 (in US dollars) is represented as:

currency = 840
amount = 4852550
amtExp10 = 2

WarrantyType is an integer. A value of zero indicates that claims
against the warranty will be aggregated, and once the value of
fulfilled claims reaches the warranty currency amount, then no
further claim will be fulfilled. A value of one indicates that each
claim is handled independently, but no individual claim can exceed
the warranty currency amount. The CA MUST select either zero or one
for this integer value.

3. Security Considerations

The procedures and practices employed by the CA MUST ensure that the
correct values for the warranty are inserted in each issued
certificate. Relying parties and users may accept or reject a
particular certificate for an intended use based on the information
provided in warranty extension. Incorrect representation of the
actual warranty may result in otherwise avoidable warranty claims for
the CA.

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RFC 4059 Warranty Certificate Extension May 2005

4. IANA Considerations

Certificate extensions and extended key usage values are identified
by object identifiers (OIDs). The OIDs used in this document are
derived from X.509 [X.509-97]. No further action by the IANA is
necessary for this document or any anticipated updates.

5. ASN.1 Module

WarrantyExtn
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-warranty-extn(27) }

DEFINITIONS IMPLICIT TAGS ::=
BEGIN

-- OID Arcs

id-pe OBJECT IDENTIFIER ::=
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) 1 }

-- Warranty Extension

id-pe-warranty-extn OBJECT IDENTIFIER ::= { id-pe 16 }

Warranty ::= CHOICE {
none NULL, -- No warranty provided
wData WarrantyData } -- Explicit warranty

WarrantyData ::= SEQUENCE {
base WarrantyInfo,
extended WarrantyInfo OPTIONAL,
tcURL TermsAndConditionsURL OPTIONAL }

WarrantyInfo ::= SEQUENCE {
validity WarrantyValidityPeriod,
amount CurrencyAmount,
wType WarrantyType }

WarrantyValidityPeriod ::= CHOICE {
sameAsCertificate NULL,
explicitPeriod ValidityPeriod }

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RFC 4059 Warranty Certificate Extension May 2005

ValidityPeriod ::= SEQUENCE {
notBefore GeneralizedTime,
notAfter GeneralizedTime }

-- CurrencyAmount specifies the currency and a monetary value.
-- Currency codes are defined in [ISO4217]. The monetary value
-- is: amount / (10 ** amtExp10), and the exponent MUST be the
-- minor unit of currency specified in [ISO4217].

CurrencyAmount ::= SEQUENCE {
currency INTEGER (1..999),
amount INTEGER (0..MAX),
amtExp10 INTEGER (0..MAX) }

WarrantyType ::= INTEGER {
aggregated (0),
perTransaction (1) }

TermsAndConditionsURL ::= IA5String

END

6. Normative References

[ISO4217] ISO. "Codes for the Representation of Currencies and
Funds", ISO 4217. 1995.

[PROFILE] Housley, R., Ford, W., Polk, W., and D. Solo, "Internet
X.509 Public Key Infrastructure Certificate and CRL
Profile", RFC 2459, January 1999.

[URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, RFC
3986, January 2005.

[X.208-88] CCITT. Recommendation X.208: Specification of Abstract
Syntax Notation One (ASN.1). 1988.

[X.209-88] CCITT. Recommendation X.209: Specification of Basic
Encoding Rules for Abstract Syntax Notation One (ASN.1).
1988.

7. Informative References

[X.509-97] ITU-T. Recommendation X.509: The Directory-
Authentication Framework. 1997.

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RFC 4059 Warranty Certificate Extension May 2005

Acknowledgements

This document was developed with the expertise and support of Russ
Housley, Vigil Security LLC, and Dr. Adrian McCullagh, Freehills
Australia.

Authors' Addresses

Duane Linsenbardt
SPYRUS
2355 Oakland Road
Suite 1
San Jose CA 95131
USA

EMail: [email protected]

Sue Pontius
SPYRUS
2355 Oakland Road
Suite 1
San Jose CA 95131
USA

EMail: [email protected]

Alice Sturgeon
SPYRUS
Suite 1502, 222 Queen St.,
Ottawa ON K0A 2T0
Canada

EMail: [email protected]

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RFC 4059 Warranty Certificate Extension May 2005

Full Copyright Statement

Copyright (C) The Internet Society (2005).

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