1 Introduction In the first part of this paper, we will discuss the concept of abstract blockchains and the implementation of a self-amending crypto-ledger. In the second part, we will describe our proposed seed protocol. 2 Self-amending cryptoledger Ablockchain protocol can be decomposed into three distinct protocols: - The network protocol discovers blocks and broadcasts transactions. - The transaction protocol specifies what makes a transaction valid. - The consensus protocol forms consensus around a unique chain. Tezos implements a generic network shell. This shell is agnostic to the transaction protocol and to the consensus protocol. We refer to the transaction protocol and the consensus protocol together as a “blockchain protocol”. We will first give a mathematical representation of a blockchain protocol and then describe some of the implementation choices in Tezos. 2.1 Mathematical representation Ablockchainprotocol is fundamentally a monadic implementation of concurrent mutations of a global state. This is achieved by defining “blocks” as operators acting on this global state. The free monoid of blocks acting on the genesis state forms a tree structure. A global, canonical, state is defined as the minimal leaf for a specified ordering. This suggests the following abstract representation: - Let (S,≤) be a totally ordered, countable, set of possible states. - Let ⊘ ∈/ S represent a special, invalid, state. S∪{⊘} S - Let B ⊂ S be the set of blocks. The set of valid blocks is B ∩ S . The total order on S is extended so that ∀s ∈ S,⊘ < s. This order deter- mines which leaf in the block tree is considered to be the canonical one. Blocks in B are seen as operators acting on the state. 1 All in all, any blockchain protocol (be it Bitcoin, Litecoin, Peercoin, Ethereum, Cryptonote, etc) can be fully determined by the tuple: ( S∪{⊘}) S,≤,⊘,B⊂S 1 GHOST is an approach which orders the leafs based on properties of the tree. Such an approach is problematic for both theoretical and practical reasons. It is almost always better to emulate it by inserting proofs of mining in the main chain. 3