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Algorand Specifications

Before an object is input to some cryptographic function, it is prepended with a multi-character domain-separating prefix.

All domain separators must be “prefix-free” (that is, they must not be concatenated).

The list below specifies each prefix:

• For cryptographic primitives:
  • OT1 and OT2: The first and second layers of keys used for ephemeral signatures.
  • MA: An internal node in a Merkle tree.
  • MB: A bottom leaf in a vector commitment.
  • KP: Is a public key used by the Merkle Signature Scheme.
  • spc: A coin used as part of the state proofs construction.
  • spp: Participant’s information (state proof public key and weight) used for state proofs.
  • sps: A signature from a specific participant used for state proofs.
• In the Algorand Ledger:
  • BH: A Block Header.
  • BR: A Balance Record.
  • GE: A Genesis configuration.
  • spm: A State Proof message.
  • STIB: A SignedTxnInBlock that appears as part of the leaf in the Merkle tree of transactions.
  • TL: A leaf in the Merkle tree of transactions.
  • TX: A Transaction.
  • SpecialAddr: A prefix used to generate designated addresses for specific functions, such as sending state proof transactions.
• In the Algorand Byzantine Fault Tolerance protocol:
  • AS: An Agreement Selector, which is also a VRF input.
  • CR: A Credential.
  • SD: A Seed.
  • PL: A Payload.
  • PS: A Proposer Seed.
  • VO: A Vote.
• In other places:
  • arc: ARCs-related hashes https://github.com/algorandfoundation/ARCs. The prefix for ARC-XXXX should start with arcXXXX (where XXXX is the 0-padded number of the ARC). For example, ARC-0003 can use any prefix starting with arc0003.
  • MX: An arbitrary message used to prove ownership of a cryptographic secret.
  • NPR: A message that proves a peer’s stake in an Algorand networking implementation.
  • TE: An arbitrary message reserved for testing purposes.
  • Program: A TEAL bytecode program.
  • ProgData: Data that is signed within TEAL bytecode programs.

Auctions are deprecated; however, their prefixes are still reserved in code:

• aB: A Bid.
• aD: A Deposit.
• aO: An Outcome.
• aP: Auction parameters.
• aS: A Settlement.