NSString * currentlLoginEmailAddress = @"[email protected]"; // Unique string use as alias for Keypairs
  NSString * bundleID = @"com.myCompany.myApp"; // Bundle ID of your App use as Application Tag
  NSString * userName = @"user name"; // User Name or name for organization which use in Certificate
  NSString * randomNumber = @"453963013"; // Any Serial number which use in Certificate.

  KeyPairAttributes * keyPairAttributes = [[KeyPairAttributes alloc] init];
  keyPairAttributes.keyLabel = currentlLoginEmailAddress;
  keyPairAttributes.keySize = KeyPairAttributes.keySize256;
  keyPairAttributes.keyStorageType = KeyPairAttributes.Hardware;
  keyPairAttributes.keyType = KeyPairAttributes.EC;
  keyPairAttributes.keyApplicationTag = bundleID;

  KeyPairManager * keypairManager = [[KeyPairManager alloc] init];
  //delete old keypair with same alias if exist.
  [keypairManager deleteKeyPairWithKeyTag:currentlLoginEmailAddress];
  //generate keypair from keypair attributes
  [keypairManager generateKeyPair:keyPairAttributes completionHandler:^(OSStatus status) {
  //get private key with alias and prompt message that will appear in Touch ID dialog.
      SecKeyRef privateKey = [keypairManager getPrivateKeyWithKeyTag:currentlLoginEmailAddress prompotMessage:@""];
      if (privateKey != nil) {
    // get public in data format 
        NSData * publicKeyData = [keypairManager getPublicKeyWithKeyTag:currentlLoginEmailAddress];
        
        SubjectDN * subjectDN = [[SubjectDN alloc] init];
        subjectDN.commonName = userName;
        subjectDN.serialNumber = randomNumber;
        subjectDN.emaiAddress = currentlLoginEmailAddress;
        // generate certificate with all subject with Public key in data and private key in seckeyreference format
        NSString * csr = [[CertificateManager getInstance] generateCertificateSigningRequestWithSubjectDN:subjectDN publicKeyData:publicKeyData privateKey:privateKey];
        if (csr.length > 0) {
        NSLog(@"%@",csr);
        }
    }
}];