Integrating Swift Code with CryptoKit into a Turbo Native Module (React Native 0.78)

[restarajat]

I’m building a Turbo Native Module for React Native 0.78 and need help integrating Swift code that uses the CryptoKit package.

What I’m Trying to Achieve
I have implemented HMAC-SHA256 hashing in Swift using CryptoKit, and I want to expose this function in my Turbo Native Module so it can be used in React Native.

React Native Version

• React Native: 0.78
• Using New Architecture (Fabric & TurboModules)

Swift Implementation
Here’s my Swift code:

import React
import Foundation
import CryptoKit

@objc(NativeCryptoImpl)
class NativeCryptoImpl: NSObject {
    @objc(hmac256:withKey:withResolver:withRejecter:)
    func hmac256(data: String, key: String, resolve: RCTPromiseResolveBlock, reject: RCTPromiseRejectBlock) -> Void {
        do {
            let hmacResult = try hmacX(data: data, key: key)
            resolve(hmacResult)
        } catch {
            reject("Hmac256Error", error.localizedDescription, error)
        }
    }

    private func hmacX(data: String, key: String) throws -> String {
        guard let keyData = Data(base64Encoded: key) else {
            throw NSError(domain: "Invalid Key", code: -1, userInfo: nil)
        }

        let contentData = Data(data.utf8)
        let keySymmetric = SymmetricKey(data: keyData)

        let hmac = HMAC<SHA256>.authenticationCode(for: contentData, using: keySymmetric)
        return hmac.map { String(format: "%02x", $0) }.joined()
    }
}

Objective-C Bridging (Turbo Native Module)
I’ve written the Objective-C bridge as follows:

NativeCrypto.mm

#import "NativeCrypto.h"
#import "Customer-Swift.h"

@implementation NativeCrypto

RCT_EXPORT_MODULE(NativeCrypto)

NativeCryptoImpl *nativecrypto = [[NativeCryptoImpl alloc] init];

- (std::shared_ptr<facebook::react::TurboModule>)getTurboModule:
    (const facebook::react::ObjCTurboModule::InitParams &)params
{
    return std::make_shared<facebook::react::NativeCryptoSpecJSI>(params);
}

RCT_EXPORT_METHOD(hmac256:(NSString *)data
                  withKey:(NSString *)key
                  resolver:(RCTPromiseResolveBlock)resolve
                  rejecter:(RCTPromiseRejectBlock)reject)
{
    [nativecrypto hmac256WithData:data key:key completion:^(NSString *result, NSError *error) {
        if (error) {
            reject(@"Hmac256Error", error.localizedDescription, error);
        } else {
            resolve(result);
        }
    }];
}

@end

NativeCrypto.h

#import <Foundation/Foundation.h>
#import <NativeCryptoSpec/NativeCryptoSpec.h>

NS_ASSUME_NONNULL_BEGIN

@interface NativeCrypto : NSObject <NativeCryptoSpec>

@end

NS_ASSUME_NONNULL_END

Issues I’m Facing

1. Swift integration in TurboModule:

   • Am I correctly exposing the Swift function through Objective-C?
   • Do I need to modify the bridging header so the Swift code works correctly with TurboModules?

2. CryptoKit Compatibility:

   • Are there any known issues or better ways to use CryptoKit inside a Turbo Native Module?

3. TurboModule Setup:

• Am I correctly registering my Swift-based implementation in NativeCrypto.mm?
• Is there anything missing in my getTurboModule implementation for RN 0.78?

What I’ve Tried

• Ensured the Swift class is exposed with @objc annotations.
• Verified the Customer-Swift.h import is generated.
• I attempted calling the module but encountered runtime errors.

Would love to get guidance on the best way to integrate Swift with TurboModules in React Native 0.78.
Thanks in advance!