Currently test flags for attestation service are passed as an extra 4 bytes data added to the 32 bytes long challenge input.

This approach is not compliant with the API definition. Challenge size can only be: 32, 48, 64 bytes.

Create a new solution where test flags are passed as part of the challenge input:

• challenge must be 64 bytes long where the first 4 byte is allocated for test flags and the rest of the bytes (4-63) must be all 0.
• The probability of collision of this special value with a real life challenge object is statistically non significant.