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CEP-18 Token Transfers and Allowances

This document describes how to transfer CEP-18 tokens on a Casper network using the Casper client. The Exploring the CEP18 Contracts documentation contains more in depth explanations on how to find the various hashes and URefs referenced throughout this document.

Transferring CEP-18 Tokens to Another Account

The following command will invoke the transfer entry point on your instance of CEP-18, directing it to transfer 10 of the associated CEP-18 tokens to another account.

casper-client put-deploy -n http://<node IP>:<PORT> \
// The chain name of the Casper network on which your CEP-18 instance was installed.
--chain-name <CHAIN NAME>\
// The local path to your account's secret key.
--secret-key ~/casper/demo/user_a/secret_key.pem \
// The contract hash of your CEP-18 contract instance.
--session-hash hash-b568f50a64acc8bbe43462ffe243849a88111060b228dacb8f08d42e26985180 \
// The name of the entry point you are invoking.
--session-entry-point "transfer" \
// The account hash of the account that you are sending CEP-18 tokens to.
--session-arg "recipient:key='account-hash-9f81014b9c7406c531ebf0477132283f4eb59143d7903a2fae54358b26cea44b" \
// The amount of CEP-18 tokens you are sending to the receiving account.
--session-arg "amount:u256='10'" \
// The gas payment you are allotting, in motes.
--payment-amount "10000000000"
Casper client command without comments 
casper-client put-deploy -n http://<node IP>:<PORT> \
--chain-name <CHAIN NAME>\
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-hash hash-b568f50a64acc8bbe43462ffe243849a88111060b228dacb8f08d42e26985180 \
--session-entry-point "transfer" \
--session-arg "recipient:key='account-hash-9f81014b9c7406c531ebf0477132283f4eb59143d7903a2fae54358b26cea44b" \
--session-arg "amount:u256='50'" \
--payment-amount "10000000000"

This command will return a deploy hash that you can query using casper-client get-deploy. Querying the Deploy allows you to verify execution success, but you will need to use the check_balance_of entry point on the utility contract to verify the account's balance.

Invoking the check_balance_of Entry Point

The following Casper client command invokes the check_balance_of entry point on the cep18_test_contract.

casper-client put-deploy -n http://<node IP>:<PORT>\
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-package-name "cep18_test_contract" \
--session-entry-point "check_balance_of" \
// This is the contract hash of your CEP-18 contract instance, passed in as an `account-hash-`.
--session-arg "token_contract:account_hash='account-hash-b568f50a64acc8bbe43462ffe243849a88111060b228dacb8f08d42e26985180'" \
// This is the account hash of the account you are checking the balance of.
--session-arg "address:key='account-hash-303c0f8208220fe9a4de40e1ada1d35fdd6c678877908f01fddb2a56502d67fd'" \
--chain-name <CHAIN NAME> \
--payment-amount 1000000000
Casper client command without comments 
casper-client put-deploy -n http://<node IP>:<PORT>\
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-package-name "cep18_test_contract" \
--session-entry-point "check_balance_of" \
--session-arg "token_contract:account_hash='account-hash-b568f50a64acc8bbe43462ffe243849a88111060b228dacb8f08d42e26985180'" \
--session-arg "address:key='account-hash-303c0f8208220fe9a4de40e1ada1d35fdd6c678877908f01fddb2a56502d67fd'" \
--chain-name <CHAIN NAME> \
--payment-amount 1000000000

After sending this command, you will need to query the results URef within the NamedKeys of your cep18_test_contract utility contract instance. More information on finding this URef can be found in the Exploring the CEP18 Contracts document.

You can use the following command to query global state for the results URef.

casper-client query-global-state -n http://<NODE IP>:<PORT> \
// This is the `results` URef location from your `cep18_test_contract` `NamedKeys`
--key uref-a46ad389b53715d9991a513c8ca48e1502facc4c563c0700a31e830c4cb8a7d4-007 \
--state-root-hash 3aecd0e4b6ec29ee7c1eed701132eabfe6e66a1e0f1595c9c65bfed447e474f7
Casper client command without comments 
casper-client query-global-state -n http://<NODE IP>:<PORT> \
--key uref-a46ad389b53715d9991a513c8ca48e1502facc4c563c0700a31e830c4cb8a7d4-007 \
--state-root-hash 3aecd0e4b6ec29ee7c1eed701132eabfe6e66a1e0f1595c9c65bfed447e474f7

This command should show something similar to the following in response, with parsed being the amount of CEP-18 tokens that the account holds.

{
  "id": -8841145064950441692,
  "jsonrpc": "2.0",
  "result": {
    "api_version": "1.0.0",
    "block_header": null,
    "merkle_proof": "[3796 hex chars]",
    "stored_value": {
      "CLValue": {
        "bytes": "010a",
        "cl_type": "U256",
        "parsed": "10"
      }
    }
  }
}

Approving an Allowance for Another Account

The Casper fungible token contract features an allowance entry point that allows an account to delegate another account to spend a preset number of CEP-18 tokens from their balance.

Approving an Account to Spend Tokens on Another Account's Behalf

The following command approves a third-party account to spend an allowance of 15 CEP-18 tokens from the balance of the account that sent the CEP-18 instance.

casper-client put-deploy -n http://<node IP>:<PORT>\
--chain-name <CHAIN NAME> \
--secret-key ~/casper/demo/user_a/secret_key.pem \
// This is the contract hash of the CEP-18 token contract.
--session-hash hash-05d893e76c731729fc26339e5a970bd79fbf4a6adf743c8385431fb494bff45e \
--session-entry-point "approve" \
// This is the account hash of the account that will receive an allowance from the balance of the account that sent the Deploy.
--session-arg "spender:key='account-hash-17192017d32db5dc9f598bf8ac6ac35ee4b64748669b00572d88335941479513'" \
// This is the number of CEP-18 tokens included in the allowance.
--session-arg "amount:u256='15'" \
--payment-amount "10000000000"
Casper client command without comments 
casper-client put-deploy -n http://<node IP>:<PORT>\
--chain-name <CHAIN NAME> \
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-hash hash-05d893e76c731729fc26339e5a970bd79fbf4a6adf743c8385431fb494bff45e \
--session-entry-point "approve" \
--session-arg "spender:key='account-hash-17192017d32db5dc9f598bf8ac6ac35ee4b64748669b00572d88335941479513'" \
--session-arg "amount:u256='15'" \
--payment-amount "10000000000"

Verifying a Previously Issued Allowance

After approving an account to spend an allowance of tokens, we can verify the allotted allowance by using the utility contract. The following command will write the allowance of the spender's account to the result URef of in the utility contract's NamedKeys:

casper-client put-deploy -n http://<node IP>:<PORT>\
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-package-name "cep18_test_contract" \
--session-entry-point "check_allowance_of" \
// This is the contract hash for the CEP-18 token.
--session-arg "token_contract:account_hash='account-hash-05d893e76c731729fc26339e5a970bd79fbf4a6adf743c8385431fb494bff45e'" \
// This is the account hash for the account that owns the CEP-18 tokens.
--session-arg "owner:key='account-hash-39f15c23df9be1244572bb499fac62cbcad3cab2dc1438609842f602f943d7d2'" \
// This is the account hash for the account previously authorized to spend an allowance of the owning account's CEP-18 tokens.
--session-arg "spender:key='account-hash-17192017d32db5dc9f598bf8ac6ac35ee4b64748669b00572d88335941479513'" \
--chain-name <CHAIN NAME> \
--payment-amount 10000000000
Casper client command without comments 
casper-client put-deploy -n http://<node IP>:<PORT>\
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-package-name "cep18_test_contract" \
--session-entry-point "check_allowance_of" \
--session-arg "token_contract:account_hash='account-hash-05d893e76c731729fc26339e5a970bd79fbf4a6adf743c8385431fb494bff45e'" \
--session-arg "owner:key='account-hash-39f15c23df9be1244572bb499fac62cbcad3cab2dc1438609842f602f943d7d2'" \
--session-arg "spender:key='account-hash-17192017d32db5dc9f598bf8ac6ac35ee4b64748669b00572d88335941479513'" \
--chain-name <CHAIN NAME> \
--payment-amount 10000000000

The following command queries global state to return the value stored under the result URef:

casper-client query-global-state -n http://<node IP>:<PORT> \
// This is the previously identified `result` URef from the utility contract's `NamedKeys`
--key uref-a46ad389b53715d9991a513c8ca48e1502facc4c563c0700a31e830c4cb8a7d4-007 \
--state-root-hash e64f877f65df26db74300bb175c244d589bd88a23b91abf9ceb73ac5e65e90f1
Casper client command without comments 
casper-client query-global-state -n http://<node IP>:<PORT> \
--key uref-a46ad389b53715d9991a513c8ca48e1502facc4c563c0700a31e830c4cb8a7d4-007 \
--state-root-hash e64f877f65df26db74300bb175c244d589bd88a23b91abf9ceb73ac5e65e90f1

You should get a response similar to the following:

{
  "id": -9142472925449984061,
  "jsonrpc": "2.0",
  "result": {
    "api_version": "1.0.0",
    "block_header": null,
    "merkle_proof": "[3796 hex chars]",
    "stored_value": {
      "CLValue": {
        "bytes": "010f",
        "cl_type": "U256",
        "parsed": "15"
      }
    }
  }
}

Transferring Tokens from an Allowance

The following command allows an account to transfer CEP-18 tokens held by another account up to their approved allowance.

casper-client put-deploy -n http://<NODE IP>:<PORT> \
--chain-name <CHAIN NAME> \
// This is the secret key for the account that is spending their `allowance` from another account's balance.
--secret-key ~/casper/demo/user_a/secret_key.pem \
// This is the CEP-18 token contract.
--session-hash hash-05d893e76c731729fc26339e5a970bd79fbf4a6adf743c8385431fb494bff45e \
--session-entry-point "transfer_from" \
// This is the account hash of the account that holds the CEP-18 in their balance.
--session-arg "owner:key='account-hash-39f15c23df9be1244572bb499fac62cbcad3cab2dc1438609842f602f943d7d2'" \
// This is the account hash of the account that will receive the transferred CEP-18 tokens.
--session-arg "recipient:key='account-hash-17192017d32db5dc9f598bf8ac6ac35ee4b64748669b00572d88335941479513'" \
// This is the amount of tokens to be transferred. If this amount exceeds the `allowance` of the account sending the Deploy, it will fail.
--session-arg "amount:u256='10'" \
--payment-amount "10000000000"
Casper client command without comments 
casper-client put-deploy -n http://<NODE IP>:<PORT> \
--chain-name <CHAIN NAME> \
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-hash hash-05d893e76c731729fc26339e5a970bd79fbf4a6adf743c8385431fb494bff45e \
--session-entry-point "transfer_from" \
--session-arg "owner:key='account-hash-39f15c23df9be1244572bb499fac62cbcad3cab2dc1438609842f602f943d7d2'" \
--session-arg "recipient:key='account-hash-17192017d32db5dc9f598bf8ac6ac35ee4b64748669b00572d88335941479513'" \
--session-arg "amount:u256='10'" \
--payment-amount "10000000000"

Increasing and Decreasing an Allowance

Increasing an Allowance

The following command increases the designated allowance for the provided account.

casper-client put-deploy -n http://<NODE IP>:<PORT> \
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-package-name "cep18_contract_package_CEP18" \
--session-entry-point "increase_allowance" \
// This is the account hash of the previously authorized allowance account.
--session-arg "spender:key='account-hash-683f53f56926f54ef9584b07585b025c68415dc05f7b2e56749153574b83d5cd'" \
// This is the additional number of CEP-18 tokens that the authorized account may spend.
--session-arg "amount:U256='10'" \
--chain-name <CHAIN NAME> \
--payment-amount 1000000000
Casper client command without comments 
casper-client put-deploy -n http://<NODE IP>:<PORT> \
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-package-name "cep18_contract_package_CEP18" \
--session-entry-point "increase_allowance" \
--session-arg "spender:key='account-hash-683f53f56926f54ef9584b07585b025c68415dc05f7b2e56749153574b83d5cd'" \
--session-arg "amount:U256='10'" \
--chain-name <CHAIN NAME> \
--payment-amount 1000000000

Decreasing an Allowance

The following command decreases the designated allowance for the provided account.

casper-client put-deploy -n http://<NODE IP>:<PORT> \
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-package-name "cep18_contract_package_CEP18" \
--session-entry-point "decrease_allowance" \
// This is the account hash of the previously authorized allowance account.
--session-arg "spender:key='account-hash-683f53f56926f54ef9584b07585b025c68415dc05f7b2e56749153574b83d5cd'" \
// This is the additional number of CEP-18 tokens that the authorized account may spend.
--session-arg "amount:U256='10'" \
--chain-name <CHAIN NAME> \
--payment-amount 1000000000
Casper client command without comments 
casper-client put-deploy -n http://<NODE IP>:<PORT> \
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-package-name "cep18_contract_package_CEP18" \
--session-entry-point "decrease_allowance" \
--session-arg "spender:key='account-hash-683f53f56926f54ef9584b07585b025c68415dc05f7b2e56749153574b83d5cd'" \
--session-arg "amount:U256='10'" \
--chain-name <CHAIN NAME> \
--payment-amount 1000000000

Minting and Burning Additional CEP-18 Tokens

Minting Additional Tokens

If the contract allows for minting, the following command will mint a number of CEP-18 tokens directly to the provided account. This increases the total supply of the token in question.

casper-client put-deploy -n http://<NODE IP>:<PORT> \
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-package-name "cep18_contract_package_CEP18" \
--session-entry-point "mint" \
// This is the account that will receive the newly minted CEP-18 tokens.
--session-arg "owner:key='account-hash-683f53f56926f54ef9584b07585b025c68415dc05f7b2e56749153574b83d5cd'" \
// This is the number of additional CEP-18 tokens to add to the total supply.
--session-arg "amount:U256='10'" \
--chain-name <CHAIN NAME> \
--payment-amount 1000000000
Casper client command without comments 
casper-client put-deploy -n http://<NODE IP>:<PORT> \
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-package-name "cep18_contract_package_CEP18" \
--session-entry-point "mint" \
--session-arg "owner:key='account-hash-683f53f56926f54ef9584b07585b025c68415dc05f7b2e56749153574b83d5cd'" \
--session-arg "amount:U256='10'" \
--chain-name <CHAIN NAME> \
--payment-amount 1000000000

Burning Tokens

If the contract allows for burning, the following command will burn a number of CEP-18 tokens directly from the provided account. This decreases the total supply of the token in question.

casper-client put-deploy -n http://<NODE IP>:<PORT> \
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-package-name "cep18_contract_package_CEP18" \
--session-entry-point "burn" \
// This is the account that the tokens will be burned from.
--session-arg "owner:key='account-hash-683f53f56926f54ef9584b07585b025c68415dc05f7b2e56749153574b83d5cd'" \
// This is the number of CEP-18 tokens to remove from the total supply.
--session-arg "amount:U256='10'" \
--chain-name <CHAIN NAME> \
--payment-amount 1000000000
Casper client command without comments 
casper-client put-deploy -n http://<NODE IP>:<PORT> \
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-package-name "cep18_contract_package_CEP18" \
--session-entry-point "burn" \
// This is the account that the tokens will be burned from.
--session-arg "owner:key='account-hash-683f53f56926f54ef9584b07585b025c68415dc05f7b2e56749153574b83d5cd'" \
// This is the number of CEP-18 tokens to remove from the total supply.
--session-arg "amount:U256='10'" \
--chain-name <CHAIN NAME> \
--payment-amount 1000000000

Changing Account Security Permissions

The change_security entrypoint can be used by an account with admin access to alter the security level of other accounts as described here.

There are five security levels, with the strongest level taking precedence over any other assigned levels. In order of highest strength to lowest:

  1. None - None overrides other security levels and removes all admin, minting and burning access of an account.

  2. Admin - Allows the account full access and control over the CEP-18 contract.

  3. MintAndBurn - Allows the account to mint new tokens and burn existing tokens.

  4. Burner - The account can burn tokens.

  5. Minter - The account can mint new tokens.

Here is an example of a session-arg that provides a list of account hashes to be included on the mint_and_burn_list:

--session-arg "mint_and_burn_list:string='account-hash-1ed5a1c39bea93c105f2d22c965a84b205b36734a377d05dbb103b6bfaa595a7,account-hash-0ea7998b2822afe5b62b08a21d54c941ad791279b089f3f7ede0d72b477eca34,account-hash-e70dbca48c2d31bc2d754e51860ceaa8a1a49dc627b20320b0ecee1b6d9ce655'"

Be aware that removing all admin accounts will lock out all admin functionality.

The following command can be supplied with any of the optional arguments above:

casper-client put-deploy -n http://<NODE IP>:<PORT> \
--secret-key ~/casper/demo/user_a/secret_key.pem \
--session-package-name "cep18_contract_package_CEP18" \
--session-entry-point "change_security" \
/// The following arguments are all optional and each consists of a string of the account hashes to be added to the list specified, separated by commas.
--session-arg "none_list:string:'<List of account hashes>'" \
--session-arg "admin_list:string:'<List of account hashes>'" \
--session-arg "mint_and_burn_list:string:'<List of account hashes>'" \
--session-arg "burner_list:string:'<List of account hashes>'" \
--chain-name <CHAIN NAME> \
--payment-amount 1000000000

Next Steps