curl --request POST \
  --url https://api.openformat.tech/key/challenge \
  --header 'Content-Type: application/json' \
  --data '
{
  "public_address": "0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266"
}
'

{
  "status": "success",
  "challenge": "b1c2903bea5b294543e751b1742256e7bd44002f6460c6b2a1f8643984d5b513"
}