Yesterday I submitted my diploma thesis. The topic was "Design of a Public Key Infrastructure Based on Decentralized Trust Management in Peer-to-Peer Networks". I came up with a mechanism that enables transaction processing between two peers in a P2P Network. After a transaction was processed the committer can prove that the transaction was commited and the temporary transaction server can prove that the committer did, indeed, want to process that particular transaction.
Unfortunately, the whole thing is in german, which basically means that nobody is going to read it