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LAMPS CMS attribute algorithm identifier This document updates RFC 3161. It adds a requirement to ensure that the id-ct-TSTInfo content type is used to align with the best practices for signed attributes with CMS signed-data. In addition, cross-protocol attacks are prevented by requiring that the Time Stamp Authority (TSA) dedicate the signature key pair to the time-stamping service.

Introduction This document updates . It adds a requirement to ensure that the id-ct-TSTInfo content type is used to align with the best practices for signed attributes with CMS signed-data . In addition, cross-protocol attacks are prevented by requiring that the Time Stamp Authority (TSA) dedicate the signature key pair to the time-stamping service.

Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.

Update to Section 4 of RFC 3161 Section 2.1 of correctly requires that the time-stamping service use a key exclusively for signing time-stamp tokens. It says: However, in real-world deployments, it has been reported that the same key pair has been used to sign time-stamp tokens of various similar formats, which creates the possibility for cross-protocol attacks. ADD:

Update to Section 2.4.2 of RFC 3161 OLD: NEW: Note that is updated to reference the most recent specification.

IANA Considerations No IANA registry updates are needed.

Security Considerations The above addition to the Security Considerations of is intended to ensure that implementations do not use a signature private key that is used to sign a time-stamp token for any other purpose.

References Normative References This document describes the format of a request sent to a Time Stamping Authority (TSA) and of the response that is returned. It also establishes several security-relevant requirements for TSA operation, with regards to processing requests to generate responses. [STANDARDS-TRACK] This document describes the Cryptographic Message Syntax (CMS). This syntax is used to digitally sign, digest, authenticate, or encrypt arbitrary message content. [STANDARDS-TRACK] In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Informative References CryptoNext Security MTG AG The Cryptographic Message Syntax (CMS) has different signature verification behaviour based on whether signed attributes are present or not. This results in a potential existential forgery vulnerability in CMS and protocols which use CMS. This document describes the vulnerability and lists mitigations and best practices to avoid it. This document updates RFC 5652 by prohibiting the use of the id-data content type for new uses of the CMS SignedData type.

Acknowledgments Thanks to Tom Tervoort for being the first person to spot the need for improvements in .