curl --request POST \
  --url https://api.privy.io/v1/wallets/{wallet_id}/rpc \
  --header 'Authorization: Basic <encoded-value>' \
  --header 'Content-Type: application/json' \
  --header 'privy-app-id: <privy-app-id>' \
  --data '{
  "method": "signTransaction",
  "params": {
    "transaction": "AQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABAAEDRpb0mdmKftapwzzqUtlcDnuWbw8vwlyiyuWyyieQFKESezu52HWNss0SAcb60ftz7DSpgTwUmfUSl1CYHJ91GAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAScgJ7J0AXFr1azCEvB1Y5zpiF4eXR+yTW0UB7am+E/MBAgIAAQwCAAAAQEIPAAAAAAA=",
    "encoding": "base64"
  }
}
'

{
  "method": "signTransaction",
  "data": {
    "signed_transaction": "AQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABAAEDRpb0mdmKftapwzzqUtlcDnuWbw8vwlyiyuWyyieQFKESezu52HWNss0SAcb60ftz7DSpgTwUmfUSl1CYHJ91GAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAScgJ7J0AXFr1azCEvB1Y5zpiF4eXR",
    "encoding": "base64"
  }
}