ITU-T Recommendations

Non-repudiation is the ability to prevent entities from denying that they have sent or received electronic transaction data in a telecommunication network. Recommendation ITU-T X.1159 provides a delegated non-repudiation architecture based on Recommendation ITU-T X.813 to generate non-repudiation evidence by a trusted third party (TTP) instead of a user.
Recommendation ITU-T X.813 defines six non-repudiation mechanisms: a TTP security token, security tokens and tamper-resistant modules, a digital signature, time stamping, an in-line TTP and a notary. This Recommendation complies with these six mechanisms, and the non-repudiation service can use a combination of these mechanisms to satisfy the security requirements of the application service.
In this Recommendation, a right and/or user's signing key for a non-repudiation generation delegates to a TTP, which is a central signing authority, and the central signing authority generates and verifies non-repudiation evidence using the delegated user's signing/validation key or the central signing authority's secret key/validation key. The delegated non-repudiation model in this Recommendation is capable of responding to key loss and theft, is safe in an open network, such as a mobile and cloud network, and provides convenient non-repudiation service.
This Recommendation describes the delegated non-repudiation service models and operations for each of the service models. The architecture also defines the security requirements of the delegated non-repudiation service. In this delegated non-repudiation service model, there are two types of service models that use the central signing authority's secret key and the delegated signing key.