How can I validate a Stellar address?

Question

I am currently only checking if the address is 56 chars long an if it is alphanumeric.

Is there a checksum in an address to verify it.

Are there any other rules ?

Answer 1

Stellar uses Ed25519 public/private keys. So you can research that if you want some more details.

If you're using a library (like the JS SDK) it's as simple as calling:

StrKey.isValidEd25519PublicKey(address);

If you want to see the details of how that's implemented, you can see here: https://github.com/stellar/js-stellar-base/blob/master/src/strkey.js#L110

In short: There is a version byte, a payload/data, and a checksum.

Answer 2

The previous answer is correct, but just to be a little more precise about what is going on, Stellar private keys are computed as follows. First, a 35-byte value is computed as follow:

• The fist byte is 'S' << 3.
• The next 32 bytes are the Ed25519 private key seed
• The last two bytes are a CRC16 checksum of the first 33 bytes.

Then the whole thing is encoded using RFC4648 base-32 encoding.

Answer 3

In a <form>, one can use a simple regexp to match the Secret Key value:

    <form onSubmit={onSubmit}>
      <label>Secret Key: </label>
      <input 
    type='text' id='secretKey' required 
    pattern='^S[0-9A-Z]{55}$' 
      title='^S[0-9A-Z]{55}$'
      />  
      <button type="submit"> Store</button>
    </form>
...
  const onSubmit = event => {
    event.preventDefault()
    alert(event.target.secretKey.value)
  }