Abstract by anuja a sonalker on Asymmetric Key Distribution

Chapter 3 
 
Asymmetric Key Distribution 
Generic threshold key generation schemes ensure that all the participants are peers in 
terms of their private-key shares. All of them can combine their shares in a similar 
manner with no restriction or compulsion in participation. This also ensures that there 
exists no monopoly or no centralized threat to the scheme. In a scheme with threshold t, 
any t of the total servers can combine to form a valid signature. The validity of the 
signature is not governed particularly by the identity of the participating servers but 
simply by their numbers. While for most public-key systems this will be ok, it will cause 
a lot of trust-related issues to come up in systems where semi-trusting parties try to form 
a meaningful alliance. In such a scenario, it will be wiser to have a Special Server who 
keeps a check on what is being signed by the group. This Special Server will have the 
extra ability to approve every certificate being collectively signed by all the servers. None 
of the servers will be able to create a valid signature on their own without the signature 
share of the Special Server.
In order to provide such authority to the Special Server, it is to be ensured that even if all 
the share servers were to cheat and try to sign a request illegitimately; they will not be 
able to do so by virtue of their shares. Their shares, under no circumstances will be able 
to reproduce the Special Server’s share. In other words, the servers are no longer peers; 
the share distribution scheme is no longer symmetric. 
Asymmetric key distribution is an algorithm to ensure that the keys generated for such a 
scenario will not be symmetric and that authoritative power will remain in the hands of 
one Special Server. It ensures that no certificate can be signed legitimately without the 

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signature of the Special Server.  The strength of the algorithm comes from the efficient 
generation and distribution of the asymmetric key-shares. This maybe done with or 
without the use of a trusted Third Party or Honest Dealer. In the honest dealer case, the 
Trusted Dealer generates the appropriate shares and distributes them to the concerned 
players before the start of the certificate signing procedure. Every share server possesses 
its shares well before they start signing certificates in the system. Without an honest 
dealer, the share servers cooperatively generate their respective shares before a certificate 
signing transaction.
Here we introduce a model of the system to facilitate better understanding of the 
algorithm. The details of the algorithm are discussed in the following sections.
3.1 The Model: 
Share 
Share 
Server 2
Server 3 
Special 
Server share
Share
Server 1 
Share 
Share 
Server 5
Server 4