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源代码是用 Java 编写的，用于原生 Android 开发。


第 1 步： 实施 ECC 库

在 .../android/app 的 build.gradle 中实现 ECC 库。

android {
    ...
    defaultConfig {
        ...
        multiDexEnabled true
    }

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8 
        targetCompatibility JavaVersion.VERSION_1_8
    }

    packagingOptions {
        exclude 'META-INF/DEPENDENCIES' 
        exclude 'META-INF/LICENSE.md'
        exclude 'META-INF/NOTICE.md'
    }
    ...
}

dependencies {
    ...
    // Crypto
    implementation 'com.nimbusds:nimbus-jose-jwt:8.9' 
    implementation 'org.bouncycastle:bcprov-jdk15on:1.64'
    ...
}

第 2 步： 声明输入

声明请求中的所有输入参数并创建 JSON 字符串。

销售请求参数
public void receiveMessage(ReadableMap data) {
    String msgVer = data.getString("msgVer");
    String pmtType = data.getString("pmtType");
    String callerDevice = data.getString("callerDevice");
    String callerDeviceVer = data.getString("callerDeviceVer");
    String txnID = UUID.randomUUID().toString().replaceAll("-", "").toUpperCase();
    String txnDateTime = data.getString("txnDateTime");
    String email = data.getString("email");
    String password = data.getString("password");
    String crcyCde = data.getString("crcyCde");
    String amt = data.getString("amt");
    String isOptInPrintReceipt = data.getString("isOptInPrintReceipt");
    String isOptInSendEReceipt = data.getString("isOptInSendEReceipt");
    String isOptInEReceipt = data.getString("isOptInEReceipt");
    String isOptInPmtAckmnt = data.getString("isOptInPmtAckmnt");
    String desc = data.getString("desc");

    String jsonMessage = "{'TxnTyp' : '" + TestPos.TransactionType.STX +
            "', 'MsgVer' : '" + msgVer +
            "', 'PmtType' : '" + pmtType +
            "', 'CallerDeviceType' : '" + callerDevice +
            "', 'CallerDeviceVer' : '" + callerDeviceVer +
            "', 'TxnID' : '" + txnID +
            "', 'LocalTxnDTTime' : '" + txnDateTime +
            "', 'Email' : '" + email +
            "', 'Pwd' : '" + password +
            "', 'AmtTxn' : '" + amt +
            "', 'CrcyTxn' : '" + crcyCde +
            "', 'OptInPrintReceipt' : '" + isOptInPrintReceipt +
            "', 'OptInSendEReceipt' : '" + isOptInSendEReceipt +
            "', 'OptInEReceipt' : '" + isOptInEReceipt +
            "', 'OptInPmtAckmnt' : '" + isOptInPmtAckmnt +
            "', 'Description' : '" + desc + "'}";

    ECKey publicKeyASJWK = new ECKey.Builder(Curve.P_256, thirdAppPublicKey)
            .keyID(UUID.randomUUID().toString())
            .build();

    String jsonMessageEncrypted = UtilCrypto.encryptWithFormatJWE(txnID,
            publicKeyASJWK.toJSONString(), secretKey, JWEAlgorithm.DIR, jsonMessage);

    startActivity(REQ_SALE, jsonMessageEncrypted);
}

第 3 步： 加密字符串

获取字符串形式的jsonMessage后，使用encryptWithFormatJWE函数对其进行加密。

在 UtilCrypto.java 中
public static String encryptWithFormatJWE(String transactionID, String sdkPublicKeyAsJWK, SecretKey secretKey, JWEAlgorithm jweAlgorithm, String message) {
    String encryptedMessage = "";

    try {
        //header
        JWEHeader.Builder builder = new JWEHeader.Builder(jweAlgorithm, EncryptionMethod.A128CBC_HS256);
        if (!TextUtils.isEmpty(transactionID)) {
            builder.keyID(transactionID);
        }
        if (!TextUtils.isEmpty(sdkPublicKeyAsJWK)) {
            builder.ephemeralPublicKey(ECKey.parse(sdkPublicKeyAsJWK));
        }
        JWEHeader header = builder.build();

        //encrypt
        if(jweAlgorithm == JWEAlgorithm.DIR) {
            Provider bouncyCastleProvider = BouncyCastleProviderSingleton.getInstance();
            Security.addProvider((bouncyCastleProvider));
            JWEObject jweObject = new JWEObject(header, new Payload(message));
            jweObject.encrypt(new DirectEncrypter(secretKey));
            encryptedMessage = jweObject.serialize();
        } else if (jweAlgorithm == JWEAlgorithm.ECDH_ES) {
            // build JWE structure
            JWECryptoParts jweParts = ContentCryptoProvider.encrypt(header, message.getBytes(), secretKey, null, new JWEJCAContext());

            // JWE Protected Header
            StringBuilder stringBuilder = new StringBuilder(header.toBase64URL().toString());
            stringBuilder.append('.');

            // Encrypted Key
            if (jweParts.getEncryptedKey() != null) { 
                stringBuilder.append(jweParts.getEncryptedKey().toString());
            }
            stringBuilder.append('.');

            // Initialization Vector
            if (jweParts.getInitializationVector() != null) {
                stringBuilder.append(jweParts.getInitializationVector().toString());
            }
            stringBuilder.append('.');

            // Ciphertext
            stringBuilder.append(jweParts.getCipherText().toString());
            stringBuilder.append('.');

            // Authentication Tag
            if (jweParts.getAuthenticationTag() != null) {
                stringBuilder.append(jweParts.getAuthenticationTag().toString());
            }
            encryptedMessage = stringBuilder.toString();
        } else {
            Log.d("Tag", "Unsupported other algorithms");
        }
    } catch (Exception ex) {
        ex.printStackTrace();
    }
    return encryptedMessage;
}

第 4 步： 使用 INTENT 执行应用程序到应用程序的调用

要使用 INTENT，Kayaaku POS 应用程序和商家的 POS 应用程序必须安装在同一设备上。

按照下面的示例代码使用startActivityForResult()。

INTENT
// start intent activity
private void startActivity (int messageType, String encryptedMessage) {
    if (messageType == REQ_SALE) {
        Intent intent = new Intent(ACTION_SALE); // ACTION_SALE = "com.finexuscards.yippiepos.xxx.SALES"
        intent.putExtra("Data", encryptedMessage);
        startActivityForResult(intent, REQ_SALE); // REQ_SALE = 0
    } else if (messageType == REQ_VOID) {
        Intent intent = new Intent(ACTION_VOID); // ACTION_VOID = "com.finexuscards.yippiepos.xxx.VOID"
        intent.putExtra("Data", encryptedMessage);
        startActivityForResult(intent, REQ_VOID); // REQ_VOID = 1
    } else if (messageType == REQ_REFUND) {
        Intent intent = new Intent(ACTION_REFUND); // ACTION_VOID = "com.finexuscards.yippiepos.xxx.REFUND"
        intent.putExtra("Data", encryptedMessage);
        startActivityForResult(intent, REQ_REFUND); // REQ_REFUND = 2
    }
}

// get response from onActivityResult()
protected void onActivityResult(int requestCode,int resultCode,Intent data){
    super.onActivityResult(requestCode,resultCode,data);
    String encryptedResponse = data.getStringExtra("Data");
}

第 5 步： 私钥和公钥

第 5.1 步： 生成密钥

生成公钥和私钥。

import java.io.FileOutputStream;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.spec.ECGenParameterSpec;
import java.util.Base64;

public void generateECCKeys(String outputPath) {
    try {
        KeyPairGenerator kpg = KeyPairGenerator.getInstance("EC");
        pg.initialize(new ECGenParameterSpec("secp256r1"), new SecureRandom());
        KeyPair keyPair = kpg.generateKeyPair();
        saveKeyPair(outputPath, keyPair);
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

public void saveKeyPair(String outputPath, KeyPair keyPair) {
    PrivateKey privateKey = keyPair.getPrivate();
    PublicKey publicKey = keyPair.getPublic();
    try {
          
        StringBuilder content = new StringBuilder();
        FileOutputStream fos = new FileOutputStream(outputPath + "./public.key");
        content.append(Base64.getEncoder().encodeToString(publicKey.getEncoded()));
        content.insert(0, "-----BEGIN PUBLIC KEY-----\n");
        content.insert(content.length(), "\n-----END PUBLIC KEY-----");
        fos.write(content.toString().getBytes());
        fos.close();
        content.setLength(0);
        fos = new FileOutputStream(outputPath + "./private.key");
        content.append(Base64.getEncoder().encodeToString(privateKey.getEncoded()));
        content.insert(0, "-----BEGIN PRIVATE KEY-----\n");
        content.insert(content.length(), "\n-----END PRIVATE KEY-----");
        fos.write(content.toString().getBytes());
        fos.close();
         
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}


第 5.2 步： 初始化按键

初始化将用于加密和解密过程的密钥。

TestPos(ReactApplicationContext reactContext) {
    super(reactContext);
    this.reactContext = reactContext;
    try {
        thirdAppPrivateKey = UtilCrypto.loadECPrivateKey(reactContext.getAssets().open("thirdapp_private_key.key"));
        thirdAppPublicKey = UtilCrypto.loadECPublicKey(reactContext.getAssets().open("thirdapp_public_key.key"));
        yippiePosPublicKey = UtilCrypto.loadECPublicKey(reactContext.getAssets().open("yippiepos_public_key.key"));
        String refNum = "1.0";
        secretKey = UtilCrypto.generateECDHSecret(thirdAppPrivateKey, yippiePosPublicKey, refNum);
    } catch (IOException ex) {
        ex.printStackTrace();
    }

    BA = BluetoothAdapter.getDefaultAdapter();
}

第 6 步：创建类

创建一个名为UtilCrypto的新 Java 类，用于加密和解密功能。


第 7 步： 加载初始化密钥

从密钥文件加载初始化的密钥。

对于 UtilCrypto.java 中的私钥
public static ECPrivateKey loadECPrivateKey(InputStream certFile) {
    ECPrivateKey ecPrivateKey = null;
    PrivateKey privateKey = null;
    try {
        byte[] encodedPrivateKey = new byte[certFile.available()];
        certFile.read(encodedPrivateKey);
        certFile.close();
        try {
            String certFileContent = new String(encodedPrivateKey)
                    .replace("-----BEGIN CERTIFICATE-----", "")
                    .replace("-----END CERTIFICATE-----","")
                    .replace("-----BEGIN PRIVATE KEY-----", "")
                    .replace("-----END PRIVATE KEY-----", "");
            encodedPrivateKey = android.util.Base64.decode(certFileContent, android.util.Base64.DEFAULT);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        PKCS8EncodedKeySpec privateKeySpec = new PKCS8EncodedKeySpec(encodedPrivateKey);
        KeyFactory keyFactory = KeyFactory.getInstance("EC");
        privateKey = keyFactory.generatePrivate(privateKeySpec);
    } catch (NoSuchAlgorithmException | InvalidKeySpecException | IOException e) {
        e.printStackTrace();
    }
    if (privateKey instanceof ECPrivateKey){
        ecPrivateKey = (ECPrivateKey) privateKey;
    }
    return ecPrivateKey;
}

第 8 步： 解密响应消息

使用decryptWithFormatJWE函数解密从 Kayaaku POS 应用程序检索到的响应消息。

在 UtilCrypto.java 中
public static String decryptWithFormatJWE(SecretKey secretKey, String message) {
    String decryptedMessage = "";
    try {
        // parse message to Object
        JWEObject jweObject = JWEObject.parse(message);

        // get header
        JWEAlgorithm algorithm = jweObject.getHeader().getAlgorithm();
        EncryptionMethod encryptionMethod = jweObject.getHeader().getEncryptionMethod();

        // decrypt
        if (algorithm.equals(JWEAlgorithm.DIR)) {
            if (encryptionMethod == EncryptionMethod.A128CBC_HS256 || encryptionMethod == EncryptionMethod.A128GCM) {
                Provider bouncyCastleProvider = BouncyCastleProviderSingleton.getInstance();
                Security.addProvider(bouncyCastleProvider);

                // start decrypting
                jweObject.decrypt(new DirectDecrypter(secretKey));
                decryptedMessage = jweObject.getPayload().toString();
            } else {
                Log.d("Tag", "Unsupported other encryption method:" + encryptionMethod);
            }
        } else {
            Log.d("Tag", "Unsupported other algorithms");
        }
    } catch (Exception ex) {
        Log.e("Tag", "decryptedMessage Failed:" + ex.getMessage());
        ex.printStackTrace();
    }
    return decryptedMessage;
}

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