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In the Archethic network, there are no blocks but only transactions, as each block is reduced to its atomic form - transaction with its own validation evidences.



Each validated transaction is stored as a chain than can only be updated from the last validation transaction in the chain The last transaction on a chain becomes the authoritative transaction.

Quantum resistant

For security reason, once the public key is disclosed, it is considered as expired, only the hash of the public key of the next transaction(aka address) is announced. This allows the next public key to be kept until the next transaction on the chain.

Address resolution

Any addresses of a transaction chain can be used as destination address. It's not necessary to specify the last transaction address in the chain.

Stateless transactions

Transaction are using an UTXO (Unspent Transaction Output) model so, a transaction cannot change state. There is no reality outside the validated transactions

UTXO mining

List of unspent outputs does not need to be specified by the sender of the transaction all unspent outputs will be reintegrated directly into the last transaction.

Transaction structure

  • Pending transaction

A pending transaction is a transaction that does not have validation. Its structure is described as below:

| Address | Type | Data | Previous public key | Previous signature | Origin signature |
| Content | Code | Ledger | Ownerships | Recipients |
| |
| |
|-----|-------| |-----------------|--------|
| UCO | Token | | Authorized keys | Secret |
|-----|-------| |-----------------|--------|

  • Address: Corresponds to the hash of the public key of the transaction

  • Type: Defines the functional role of the transaction

  • Data: Contains all the operations to be performed (transfers, smart contracts, key authorizations, etc.)

    • Content: Can contain any kind of data. It can be used to host some data (HTML page, text, image, code, etc.)
    • Code: Defines the smart contract code to be interpreted by the node. More details on Smart-Contracts section.
    • Ledger: Defines several types of ledger operations
      • UCO: for the cryptocurrency transfers
      • Token: for non-financial transactions (intended for P2P uses - as tokens, loyalties, etc.)
    • Ownerships: Define some cryptographic authorizations and delegations
      • Authorized keys: list of authorized keys to be able to decrypt secrets
      • Secrets: Encrypted contents which can be decrypted by the authorized keys
    • Recipients: Additional recipients to target smart contracts
  • Previous public key: Corresponds to the public key associated to the previous transaction

  • Previous signature: Corresponds to the signature of the private key associated with the mentioned previous public key

  • Origin signature: Corresponds to the signature of the device or software that generated the transaction. This is used on the Proof Of Work mechanism and is a necessary condition of its validation.

  • Validated transaction

A validated transaction is a pending transaction completed with the validation proofs required by the Heuristic Algorithms. Those are defined by the given structure:

| Validation Stamp | Cross Validation Stamps |
| |
| |-----------------|-----------|
| | Node public key | Signature |
| |-----------------|-----------|
| Timestamp | Proof of Work | Proof of Integrity | Proof of Election | Ledger Operations | Recipients | Errors | Signature |
| Fee | Transaction movements | Unspent outputs |

  • Validation Stamp: Stamp generated by the coordinator node
    • Proof of work: Corresponds to the public key matching the origin signature (More details on the Proof of Work section).
    • Proof of integrity: Proves the linkage of the previous transactions
    • Proof of election: Proves the validation node's rotating election and permit to reproduce it later (See Rotating Election)
    • Ledger operations: Contains all the ledger operations that will be taken into account by the network
      • fee: Transaction's fee
      • transaction movements: Issuer and resolved transaction movements
      • Unspent outputs: List of the remaining unspent outputs of the transaction chain after validation
    • Recipients: List of resolved addresses of the recipients
    • Errors: Any errors found in the validation (i.e. pending transaction error)
    • Signature: Cryptographic signature of the entire stamp by the coordinator's key
  • Cross validation stamps: To be considered as validated, the Validation Stamp must be joined as many Cross Validation Stamp as required by the Heuristic Algorithms. They are signatures of the given validation stamp.
    • Node public key: Correspond to the node's public key which generate this Cross Validation Stamp's signature
    • Signature: Correspond to the signature of the Cross Validation Stamp for the mentioned public key
    • Inconsistencies: In case of inconsistencies or disagreement, it will contain a list of inconsistencies noted