Addresses

Address type format

The Address data structure formats multiple cryptographic public key types.

Currently, Address public key types start out as uncompressed ECDSA secp256k1_ 64 byte binary arrays.

An Address is generated by hashing the raw bytes of the public key and appending a 4 byte checksum.

The checksum comes from the hash of the first 4 bytes of the Address.

The result is Base58 encoded.

You can generate test addresses with the the ledger-api-py(Python SDK).

Create an Address

function main()

  var account = Address("2ifr5dSFRAnXexBMC3HYEVp3JHSuz7KBPXWDRBV4xdFrqGy6R9");

endfunction

Type size in detail

There are two Address formats:

• INTERNAL: This is a straightforward canonical representation of a sha256 public key and the length is always 32 bytes. This is the Address format used inside the Fetch.ai ledger C++ code.

• EXTERNAL: This is the public format used to interact with the Python Ledger HTTP API and also in smart contract etch code. The final size of the external Address result is between 50-51 bytes as the Base58 encoding process increases the size by a multiple of 1.42.

In Python-type pseudocode below, we show you the steps for producing both types of Address.

public_key = XYZ

# simple internal representation
canonical_address = sha256(public_key)

# external representation
RAW_public_api_address = concatenate(canonical_address, sha256(canonical_address)[0 : 4bytes])

# check length
assert(36bytes == len(RAW_public_api_address))

# Base58 encoding
public_api_address = Base58(RAW_public_api_address)

SHA256

etch currently supports the SHA256 encryption algorithm. Find out more here.

Verification

The Address type has a function signedTx() which allows you to verify the signature. It returns a boolean. This is only valid in an @action function, else it will return false.

function main()

  var account = Address("2ifr5dSFRAnXexBMC3HYEVp3JHSuz7KBPXWDRBV4xdFrqGy6R9");
  var verified : Bool;
  verified = account.signedTx(); 
  printLn(toString(verified)); 

endfunction

The above code always prints false when it is not contained within an @action function.

The Address type will eventually support all asymmetric cryptographic types and, more importantly, will be quantum computing ready.

Print Address

Use toString() to print Address types.

function main()

  var account = Address("2ifr5dSFRAnXexBMC3HYEVp3JHSuz7KBPXWDRBV4xdFrqGy6R9");
  printLn(toString(account));

endfunction