Telegram is a leading instant messaging and VOIP service with over 200 million monthly active users, founded by Pavel and Nikolai Durov. In early 2018, Telegram announced a blockchain venture and raised $1.7 billion in a private SAFT token sale for Grams, the native token of the Telegram Open Network (TON). Broadly, TON’s architecture bears resemblance to projects such as Cosmos and Polkadot, as multi-chain PoS smart contract platforms. This design aims to enable more flexibility for developers, as they can use a chain custom designed for their application while remaining interoperable with others, and network-wide scalability, as computational work is localized to the particular nodes and chains who require the current state, as opposed to requiring all to validate each transaction. Ideally, this approach would offer TON considerable scalability benefits compared to previous smart contract platforms, enabling a broader set of computationally-intensive applications to be built on the platform.
The Telegram Blockchain, which comprises a key aspect of the broader Telegram Open Network, has the following characteristics:
- Byzantine Fault Tolerant Proof of Stake, in which a known subset of validators can each suggest the next block, which must be validated by a majority of the validators before being confirmed. This is in contrast to Delegated Proof of Stake (DPoS) approaches, in which there is a known order of block producing nodes. DPoS has a scheduled validator independently validate a block, while BFT involves collective validation of the proposed block before it is propagated to the rest of the (non-validator) network. Thus, by using a BFT approach in which blocks are validated before they are propogated, TON allows transaction states confirmed by one block to be immediately considered final and used in a transaction in the next block; this is a key feature for robust and atomic transactions between individual chains.
- Turing-complete smart contracts, enabling arbitrarily complex programs on-chain, written in the novel stack-based language Fift, which is similar to the existing language Forth.
- Multiple blockchains, which are:
- Mixed homogeneous and heterogeneous. Shardchains are homogeneous, in that they have the same transaction format (i.e. UTXO/Account model), virtual machine, available tokens, etc; homogeneous shardchains are directly interoperable. In contrast, TON workchains are heterogeneous, allowing each to define their own operating procedures to fit their use case.
- Sharded, in which the state and transaction processing is distributed across many chains in order to increase throughput by way of parallel processing. Other projects such as Ethereum 2.0 use a form of sharding.
- Tightly-coupled interaction between chains, defining a strict, formal specification for token transfers between chains. Polkadot does not have tightly coupled interactions between chains.
As a smart contract platform using a sharded, hierarchical architecture of many chains to increase scalability, TON has the following types of chains:
- Masterchain - the singular, top-level chain which contains current protocol parameters for the TON, the set of validators and their stakes, and the set of hashes of the most recent blocks of all workchains and sidechains.
- Workchain - many application-specific chains which perform value transfer and smart contract computation. Each workchain defines its own rules, including address and transaction format, VMs for smart contracts, and available metatokens. All workchains must satisfy the ‘tightly-coupled’ interoperability criteria in order to effectively transfer messages and transactions between one another.
- Shardchain - the smallest unit of the network, responsible for processing transactions for a subset of accounts in its related workchain. Each workchain can be sharded into many shardchains, which have the same rules as the parent. Shardchains produce lowest level blocks of transactions, which are aggregated into summary blocks by the workchains and masterchain.
Beyond the TON blockchain proper, the following components also play key roles in the network:
- Networking through a Distributed Hash Table (DHT) that aims to efficiently propagate transactions to related shardchains
- File Storage through an overlay network separate from the TON blockchain , with the ledger recording location
- Payments through a Lightning Network-like system of payment channels that increases the networks aggregate transaction capacity by taking small payments off-chain
The original supply of Grams is 5 billion; it is unclear what portion of these were sold in the private sale. Grams function as a means of payment, gas for smart contract execution, payment for persistent storage, and as a staking mechanism for both the masterchain and individual shardchains. The whitepaper indicates that validators of the masterchain will earn roughly 20% annual rewards, though full economic modeling has yet to be released. Token holders can delegate proxies who participate in consensus and both receive a proportional amount of block rewards.