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Secure and flexible Key distribution for industrial wireless devices

IP.com Disclosure Number: IPCOM000210378D
Publication Date: 2011-Aug-31
Document File: 5 page(s) / 28K

Publishing Venue

The IP.com Prior Art Database

Abstract

Distribution of cryptographic keys to communication devices is a security critical operation. Any eavesdropping or tampering on the key transmission undermines the security objective. This invention concerns a method to improve flexibility and security of key distribution. It is particularly suitable for wireless industrial communication devices.

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Secure and flexible Key distribution for industrial wireless devices

Background of the invention

Distribution of cryptographic keys to communication devices is a security critical operation. Any eavesdropping or tampering on the key transmission undermines the security objective. This invention concerns a method to improve flexibility and security of key distribution. It is particularly suitable for wireless industrial communication devices.

Problem to be solved

Cryptographic methods for device authentication and data encryption rely on some initial trusted data, which has to be downloaded into the communication devices. With symmetric key cryptographic systems, this initial trusted data is the master key (called "join key" in the Wireless HART specification [1]), a secret which is shared only with the intended communication peers. (Usually dynamic session encryption keys are derived from the master key by combining it with some random numbers.) - With asymmetric cryptographic systems, the required basic trusted data is either the public key of the communication peer, or the CA certificate of the Certification Authority which has certified the peer's public key. (The CA certificate contains the public key of the CA, to be used for verification of the peer's certificate.) The public key or the certificate are not secret, but must be authentic i.e. protected against spoofing (an attacker surreptitiously inserting or replacing the public key or certificate by a compromised value).

The loading of the initial trusted data is a security-critical bootstrapping procedure. This invention concerns methods to improve security and flexibility of downloading the initial trusted data to the communication devices.

State-of-the-art solutions

There are several methods to download the initial keys1 to communication devices:

1. Where the communication device is equipped with an human machine interface (HMI, e.g. displays, keyboards, or manual switches), key distribution can be simply done by the user entering the key manually via the HMI. This method is typically applied for wireless LAN (WLAN) devices according to the IEEE 802.11 standard, where it is known as authentication using "pre-shared" keys. Bluetooth's "device pairing" applies the same method [2][3].

2. Where a direct wired connection is available between the key generator and the device, the initial key can be directly downloaded, assuming that the link is secure while the downloading takes place. This is shown in Figure 1 between the security manager (key generator) and the gateway (peer communication device).

3. For small industrial devices without HMI, such as envisaged as industrial devices according to the Wireless HART standard [1], it is more suitable to provide a maintenance port (wired plug) on the device, to which a handheld maintenance tool (HHT) can be temporarily connected for the purpose of commissioning, in particularly for downloading the key. The HHT acts as a secure int...