Key Directory API

The SDK exchanges public keys through your backend, DropOnAir never stores encryption keys. Your backend must expose two endpoints that the SDK calls automatically. Publish requests include a stable deviceId, and multi-device clients should prefer a deviceKeys response.

Publish my public key

Called automatically by the SDK on every connect(). Body:

{ "publicKey": "BASE64_X25519_PUBLIC_KEY", "deviceId": "ios-abc-123" }

Fetch recipient keys

Preferred multi-device response:

{
  "deviceKeys": [
    { "deviceId": "ios-abc-123", "publicKey": "BASE64_X25519_PUBLIC_KEY" },
    { "deviceId": "web-def-456", "publicKey": "BASE64_X25519_PUBLIC_KEY" }
  ]
}

Legacy single-device fallback, still accepted by older client paths:

{ "publicKey": "BASE64_X25519_PUBLIC_KEY" }

Spring Boot example

@RestController
@RequestMapping("/api/droponair/keys")
public class KeyDirectoryController {

  @PutMapping("/me")
  public ResponseEntity<Void> publishKey(@AuthenticationPrincipal UserPrincipal user,
                                               @RequestBody Map<String, String> body) {
    keyStore.save(user.getId(), body.get("deviceId"), body.get("publicKey"));
    return ResponseEntity.ok().build();
  }

  @GetMapping("/{userId}")
  public Map<String, Object> getKeys(@PathVariable String userId) {
    var deviceKeys = keyStore.list(userId).stream()
      .map(key -> Map.of("deviceId", key.deviceId(), "publicKey", key.publicKey()))
      .toList();
    return Map.of("deviceKeys", deviceKeys);
  }
}