How can I verify whether an address I've created offline is valid?

Question

For security reasons I've created an IOTA address offline. Before I transfer into this address, how can I ensure this address is valid?

Answer 1

It seems like what you want to avoid is the risk that your funds will "end up somewhere which isn't in my control."

In that case, you should use the IOTA API to double-check that your seed produces your address. This will ensure that you indeed have access to funds at that address. This can be done entirely offline, using the IOTA JavaScript API and the following code:

var IOTA = require('iota.lib.js');
var iota = new IOTA({
  'provider': null
});

var seed = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
var index = 0;
var security = 2;

iota.api.getNewAddress(seed, {"index": index, "security": security, "checksum": true, "total": 1}, function(error, addr) {
  if (error) {
    console.log(error);
  } else {
    console.log("Address for seed " + seed + " at index " + index + " is: ");
    console.log(addr[0]);
  }
});

Answer 2

You can generate your address with the option checksum: true . It will give you a 90 characters address where last 9 chars are the checksum.

Before attaching this address to the tangle you can use the function

Utils.isValidChecksum(<90 chars address>)

to check that your address is valid.

source

Answer 3

• send only a small amount of IOTA or even a zero value transaction of the address
• check if you see the transaction in your wallet
• send the rest of your IOTA

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Although this would work, it shouldn't really be an issue, if you generated the address with a tool that works like the official IOTA light wallet or any of the official IOTA libraries from iotaledger because they don't make mistakes when generating addresses.

Furthermore, you may have noticed that some addresses are 90 trytes long (when IOTA addresses are really only 81 trytes long). This is because they have a 9-tryte checksum which is only in place so that human errors (when copying or transmitting) don't happen. Basically if you want to send a transaction to an address from the light wallet, it won't let you if the checksum doesn't match the address.

You might want to check, if your offline generated address has a length of 81 or 90. If it is only 81, generate it again. There is usually an option to generate it together with the checksum.