DSKPP And PSKC: IETF Standard Protocol And Payload For Symmetric Key Provisioning Philip Hoyer Senior Architect – CTO Office

Brief History of IETF Keyprov Working Group Dynamic Symmetric Key Provisioning Protocol (DSKPP) –Overview –Protocol Variants –Two- and Four-Pass Comparison –Cryptographic Properties –Binding Portable Symmetric Key Container (PSKC) Agenda

No current standard to provision symmetric keys and related meta data –over the wire –over the air –or offline (bulk) IETF Keyprov Working Group: Why?

No standard payload container for keys IETF Keyprov Working Group: Why?

No interoperability between –key clients –and key servers IETF Keyprov Working Group: Why? Application Vendor A Application Vendor B Key server Vendor A Key server Vendor B Key protocol / format B Key protocol / format A No Interoperability!

Standards –Protocol –Payload Interoperability between –key clients –and key servers IETF Keyprov Working Group: Objectives PSKC Application Vendor A Application Vendor B Key server Vendor A Key server Vendor B DSKPP Interoperability!

Description Current developments in deployment of Shared Symmetric Key (SSK) tokens have highlighted the need for a standard protocol for provisioning symmetric keys. The need for provisioning protocols in PKI architectures has been recognized for some time. Although the existence and architecture of these protocols provides a feasibility proof for the KEYPROV work assumptions built into these protocols mean that it is not possible to apply them to symmetric key architectures without substantial modification. In particular the ability to provision symmetric keys and associated attributes dynamically to already issued devices such as cell phones and USB drives is highly desirable. Founded in February 2007 with input from VeriSign (DSKPP), RSA (CT-KIP), and OATH (PSKC). IETF Keyprov Working Group

Scope –The scope of the working group shall be to define protocols and data formats necessary for provisioning of symmetric cryptographic keys and associated attributes. The group shall consider use cases related to use of Shared Symmetric Key Tokens. Other use cases may be considered for the purpose of avoiding unnecessary restrictions in the design and ensure the potential for future extensibility. Deliverables: –Dynamic Symmetric Key Provisioning Protocol ( –Portable Symmetric Key Container (XML) ( ) –Symmetric Key Package Content Type (ASN.1) ( IETF Keyprov WG: Scope and Deliverables

DSKPP is a client-server protocol for initialization (and configuration) of symmetric keys to cryptographic modules. Intended for use within computer and communications systems employing symmetric cryptographic modules that are locally (over-the-wire) or remotely (over- the-air) accessible. Can be run with or without private-key capabilities in the cryptographic modules, and with or without an established public key infrastructure. DSKPP: Overview

DSKPP variants support multiple usage scenarios: –Four-pass variant enables mutual key generation by the provisioning server and cryptographic module in near real-time; provisioned keys are not transferred over-the-wire or over-the-air –Two-pass variant enables generation and transport of symmetric keys to a cryptographic module in environments where near real-time communication is not possible –Two-pass variant also enables transport of pre-generated (e.g., legacy) keys to a cryptographic module DSKPP: Protocol Variants

DSKPP: Two-Pass and Four-Pass Comparison

Key confirmation –In both variants via MAC on exchanged data Replay protection –In both variants through inclusion of client-provided data in MAC Server authentication –In both variants through MAC in ServerFinished message when replacing existing key Protection against MITM –In both variants through use of shared keys, client certificates, or server public key usage User authentication –Enabled in both variants using authentication code Device authentication –In both variants if based on shared secret key or if device sends a client certificate DSKPP: Cryptographic Properties

Security Binding –Transport level encryption (e.g., TLS) is not required for key transport –TLS/SSL is required if other parameters/attributes must be protected in transit HTTP Binding –Special Content-Type header recommended –Examples provided in specification DSKPP: Bindings

Portable Symmetric Key container (PSKC) a standardized XML-based key container for transporting symmetric keys and key related meta data Allows transmission of key policies and key utilization purpose aligned with NIST SP Allows transmission of PIN values that protect access to keys and related PIN policy Specifies the information elements that may be required when the symmetric key is utilized for specific purposes, such as the initial counter in the [HOTP] algorithm Requests the creation of a IANA registries for: –Algorithm profiles where algorithms, their related meta-data and PSKC transmission profile can be recorded for centralized standardized reference –Key usages aligned with NIST SP (e.g. encrypt, decrypt, sign, verify, otp, etc) – ( PSKC: Overview

PSKC: Main Entities KeyContainer EncryptionKey Signature …. KeyContainer EncryptionKey Signature …. KeyPackage Key KeyPolicy Key KeyPolicy Data: Secret EncryptedValue ValueMAC Data: Secret EncryptedValue ValueMAC DeviceInfo SerialNumber Manufacturer …. DeviceInfo SerialNumber Manufacturer …. CryptoModuleInfo ID …. CryptoModuleInfo ID …. Data: Counter PlainValue Data: Counter PlainValue Data: Other

Pre-shared-key Manufacturer CM_ID_001 Issuer pgznhXdDh…. ooo0Swn6s/myD4o05FCfBHN0560= 0 OTP

Pre-shared symmetric keys –Including transmission of MAC key and value for algorithms without integrity check Password based encryption (PBE) based on XMLEncryption 1.1 DerivedKey and PKCS#5 Asymmetric (PKI) Signature of whole KeyContainer PSKC: Key Protection Mechanisms

DSKPP – Online symmetric key provisioning protocol –IETF proposed standard PSKC – XML – Online/Offline Symmetric Key transport format –IETF proposed standard Interoperable standards-based symmetric key provisioning available now! Summary

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