Chain of trust
Encyclopedia
In computer security, a chain of trust is established by validating each component of hardware
and software from the bottom up. It is intended to ensure that only trusted software and hardware can be used while still remaining flexible.
. The signing authority will only sign boot programs that enforce security, such as only running programs that are themselves signed, or only allowing signed code to have access to certain features of the machine. This process may continue for several layers.
This process results in a chain of trust. The final software can be trusted to have certain properties, because if it had been illegally modified its signature would be invalid, and the previous software would not have executed it. The previous software can be trusted, because it, in turn, would not have been loaded if its signature would have been invalid. The trustworthiness of each layer is guaranteed by the one before, back to the Trust Anchor
- the hardware.
It would be possible to have the hardware check the suitability (signature) for every single piece of software. However, this would not produce the flexibility that a "chain" provides. In a chain, any given link can be replaced with a different version to provide different properties, without having to go all the way back to the trust anchor. This use of multiple layers is an application of a general technique to improve scalability, and is analogous to the use of multiple certificates in a certificate chain
.
(CA).
The Certificate Hierarchy is a structure of certificates that allows individuals to verify the validity of a certificate's issuer. Certificates are issued and signed by certificates that reside higher in the certificate hierarchy, so the validity and trustworthiness of a given certificate is determined by the corresponding validity of the certificate that signed it.
The Chain of Trust of a Certificate Chain is an ordered list of certificates, containing an end-user subscriber certificate and intermediate certificates (that represents the Intermediate CA), that enables the receiver to verify that the sender and all intermediates certificates are trustworthy.
vision based on the Trusted Platform Module
. Although its proponents (including Microsoft
) claim many benefits from this trust, most are convinced that the primary application is Digital Rights Management
.
Hardware
Hardware is a general term for equipment such as keys, locks, hinges, latches, handles, wire, chains, plumbing supplies, tools, utensils, cutlery and machine parts. Household hardware is typically sold in hardware stores....
and software from the bottom up. It is intended to ensure that only trusted software and hardware can be used while still remaining flexible.
Introduction
A chain of trust is designed to allow multiple users to create and use software on the system, which would be more difficult if all the keys were stored directly in hardware. It starts with hardware that will only boot from software that is digitally signedDigital signature
A digital signature or digital signature scheme is a mathematical scheme for demonstrating the authenticity of a digital message or document. A valid digital signature gives a recipient reason to believe that the message was created by a known sender, and that it was not altered in transit...
. The signing authority will only sign boot programs that enforce security, such as only running programs that are themselves signed, or only allowing signed code to have access to certain features of the machine. This process may continue for several layers.
This process results in a chain of trust. The final software can be trusted to have certain properties, because if it had been illegally modified its signature would be invalid, and the previous software would not have executed it. The previous software can be trusted, because it, in turn, would not have been loaded if its signature would have been invalid. The trustworthiness of each layer is guaranteed by the one before, back to the Trust Anchor
Trust Anchor
In cryptography, a trust anchor is an authoritative entity represented via a public key and associated data. It is used in the context of public key infrastructures, X.509 digital certificates and DNSSEC....
- the hardware.
It would be possible to have the hardware check the suitability (signature) for every single piece of software. However, this would not produce the flexibility that a "chain" provides. In a chain, any given link can be replaced with a different version to provide different properties, without having to go all the way back to the trust anchor. This use of multiple layers is an application of a general technique to improve scalability, and is analogous to the use of multiple certificates in a certificate chain
Root certificate
In cryptography and computer security, a root certificate is either an unsigned public key certificate or a self-signed certificate that identifies the Root Certificate Authority . A root certificate is part of a public key infrastructure scheme...
.
Computer Security
In Computer Security, Digital certificates are verified using a chain of trust. The trust anchor for the digital certificate is the Root Certificate AuthorityCertificate authority
In cryptography, a certificate authority, or certification authority, is an entity that issues digital certificates. The digital certificate certifies the ownership of a public key by the named subject of the certificate...
(CA).
The Certificate Hierarchy is a structure of certificates that allows individuals to verify the validity of a certificate's issuer. Certificates are issued and signed by certificates that reside higher in the certificate hierarchy, so the validity and trustworthiness of a given certificate is determined by the corresponding validity of the certificate that signed it.
The Chain of Trust of a Certificate Chain is an ordered list of certificates, containing an end-user subscriber certificate and intermediate certificates (that represents the Intermediate CA), that enables the receiver to verify that the sender and all intermediates certificates are trustworthy.
Applications
One application of this mechanism is the Trusted Computing Group'sTrusted Computing Group
The Trusted Computing Group , successor to the Trusted Computing Platform Alliance , is an initiative started by AMD, Hewlett-Packard, IBM, Intel, and Microsoft to implement Trusted Computing...
vision based on the Trusted Platform Module
Trusted Platform Module
In computing, Trusted Platform Module is both the name of a published specification detailing a secure cryptoprocessor that can store cryptographic keys that protect information, as well as the general name of implementations of that specification, often called the "TPM chip" or "TPM Security...
. Although its proponents (including Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
) claim many benefits from this trust, most are convinced that the primary application is Digital Rights Management
Digital rights management
Digital rights management is a class of access control technologies that are used by hardware manufacturers, publishers, copyright holders and individuals with the intent to limit the use of digital content and devices after sale. DRM is any technology that inhibits uses of digital content that...
.