isValidPayload method
Returns true if value is a valid ivBase64:ciphertextBase64 string.
Implementation
bool isValidPayload(String value) {
final parts = value.split(':');
if (parts.length != 2) return false;
try {
base64Decode(parts[0]);
base64Decode(parts[1]);
return parts[0].isNotEmpty && parts[1].isNotEmpty;
} catch (_) {
return false;
}
}