Hello Yasir,
There is no need to protect by SigPolicyHash other fields of
SignaturePolicyId structure because it is placed in a signed attribute. All
signed attributes are protected by the signature itself.
In most cases the policy would be an external document not included in your
signed message, and you have to unambiguously indicate specific policy with
respect to which your document should be treated. E.g., you may only have an
URI pointing to the policy as a SigPolicyQualifier.
You have to hash a digital signature policy represented as a sequence of
bytes in some format and place the computed value in SigPolicyHash.
Pavel Smirnov
Crypto-Pro
Tel./Fax: +7 495 780-4820
WWW: <http://www.cryptopro.ru/> http://www.CryptoPro.ru
e-mail: <mailto:spv(_at_)CryptoPro(_dot_)ru> spv(_at_)CryptoPro(_dot_)ru
From: owner-ietf-smime(_at_)mail(_dot_)imc(_dot_)org
[mailto:owner-ietf-smime(_at_)mail(_dot_)imc(_dot_)org]
On Behalf Of Yasir Khan
Sent: Wednesday, June 25, 2008 2:43 PM
To: ietf-smime(_at_)imc(_dot_)org
Subject: Using Signature Policy in RFC-5126
We have a question related to using the signature policy in the CAdES
signatures (EPES) defined in RFC-5126. Here is the relevant structure:
SignaturePolicyId ::= SEQUENCE {
sigPolicyIdentifier SigPolicyId,
sigPolicyHash SigPolicyHash,
sigPolicyQualifiers SEQUENCE SIZE (1..MAX) OF
SigPolicyQualifierInfo OPTIONAL
}
SigPolicyId ::= OBJECT IDENTIFIER
SigPolicyHash ::= OtherHashAlgAndValue
OtherHashAlgAndValue ::= SEQUENCE {
hashAlgorithm AlgorithmIdentifier,
hashValue OtherHashValue
}
SigPolicyQualifierInfo ::= SEQUENCE {
sigPolicyQualifierId SigPolicyQualifierId,
sigQualifier ANY DEFINED BY sigPolicyQualifierId
}
SigPolicyQualifierId ::= OBJECT IDENTIFIER
id-spq-ets-uri OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-spq(5) 1
}
SPuri ::= IA5String
id-spq-ets-unotice OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-spq(5) 2
}
SPUserNotice ::= SEQUENCE {
noticeRef NoticeReference OPTIONAL,
explicitText DisplayText OPTIONAL
}
NoticeReference ::= SEQUENCE {
organization DisplayText,
noticeNumbers SEQUENCE OF INTEGER
}
DisplayText ::= CHOICE {
visibleString VisibleString (SIZE (1..200)),
bmpString BMPString (SIZE (1..200)),
utf8String UTF8String (SIZE (1..200))
}
In the given structure for CAdES-EPES signature, its is not clear that
whether are we computing the hash "SigPolicyHash" over the document at
"SPuri" and/or over the "SPUserNotice"
Are the following combinations valid?
1) Only compute hash over document present at SPURI if only SPUri is set
2) Only compute hash over SPUserNotice if only SPUserNotice is set
3) Compute hash over document at SPURI and SPUserNotice if both are set
Please clarify it. Thanks!
Regards,
Yasir Khan
Development Manager
Ascertia Ltd
40 Occam Road
Surrey Research Park
Guildford
Surrey, GU2 7YG
United Kingdom
t. +44 (0)1483 685500
f. +44 (0)1483 573704
www.ascertia.com <http://www.ascertia.com/>
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