1. A method of providing evidence of a state of a computer platform, comprising: measuring a state of the computer platform, wherein measuring a state comprises a measurement of a first data structure in the computer platform, to provide a first measured state; using the first measured state in evidence of the state of the computer platform; replacing the first data structure with a second data structure in the computer platform; measuring the state of the computer platform with the first data structure replaced by the second data structure to provide a second measured state; verifying that the second measured state is as trustworthy as the first measured state; and substituting the second measured state for the first measured state in evidence of the state of the computer platform.