How should Veraison handle multiple nonce length in one session

[cowbon]

Generally, the length of nonce is 64 bytes for TSM report. But NVML defines nonce length as 32 bytes for GPU attestation report. When we create a session, the nonce size is fixed. How does Veraison services and ratsd handle this in the composite evidence?

[THS-on]

Any harm in taking the maximum and truncating the rest?

[cowbon]

Any harm in taking the maximum and truncating the rest?

We want to avoid the loss of entropy. Depending on which part is chopped off, different amounts of entropy may be lost. In ratsd, extendable-output functions (XOF) was used for securely mapping an input of length A to an output of length B without introducing statistical biases or predictable patterns. We may close the issue once services can handle SHAKE-256 correctly.