Features of Public Key System in SET - II
To form a dual signature, convert the two messages separately into two message digests
- concatenate the two messages and form the message digest of the combination
- Use this combined message digest to form dual digital signature
If documents are 1 and 2, send document 1, digest of document 2 and dual digital signature to party that can see message 1but for whom message 2 is not be seen.
- Analogously for other party and document 2
This strategy allows one to intrinsically link messages in a legally provable fashion but confidentiality is preserved