TrivialDriveJava/app/src/main/java/com/sample/android/trivialdrivesample/billing/Security.java [46:138]:
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class Security {
    static final private String TAG = "IABUtil/Security";
    static final private String KEY_FACTORY_ALGORITHM = "RSA";
    static final private String SIGNATURE_ALGORITHM = "SHA1withRSA";

    /**
     * BASE_64_ENCODED_PUBLIC_KEY should be YOUR APPLICATION PUBLIC KEY. You currently get this
     * from the Google Play developer console under the "Monetization Setup" category in the
     * Licensing area. This build has been setup so that if you define base64EncodedPublicKey in
     * your local.properties, it will be echoed into BuildConfig.
     */

    final private static String BASE_64_ENCODED_PUBLIC_KEY = BuildConfig.BASE64_ENCODED_PUBLIC_KEY;

    /**
     * Verifies that the data was signed with the given signature
     *
     * @param signedData the signed JSON string (signed, not encrypted)
     * @param signature  the signature for the data, signed with the private key
     */
    static public boolean verifyPurchase(String signedData, String signature) {
        if ((TextUtils.isEmpty(signedData) || TextUtils.isEmpty(BASE_64_ENCODED_PUBLIC_KEY)
                || TextUtils.isEmpty(signature))
        ) {
            Log.w(TAG, "Purchase verification failed: missing data.");
            return false;
        }
        try {
            PublicKey key = generatePublicKey(BASE_64_ENCODED_PUBLIC_KEY);
            return verify(key, signedData, signature);
        } catch (IOException e) {
            Log.e(TAG, "Error generating PublicKey from encoded key: " + e.getMessage());
            return false;
        }
    }

    /**
     * Generates a PublicKey instance from a string containing the Base64-encoded public key.
     *
     * @param encodedPublicKey Base64-encoded public key
     * @throws IOException if encoding algorithm is not supported or key specification
     *                     is invalid
     */
    static private PublicKey generatePublicKey(String encodedPublicKey) throws IOException {
        try {
            byte[] decodedKey = Base64.decode(encodedPublicKey, Base64.DEFAULT);
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_FACTORY_ALGORITHM);
            return keyFactory.generatePublic(new X509EncodedKeySpec(decodedKey));
        } catch (NoSuchAlgorithmException e) {
            // "RSA" is guaranteed to be available.
            throw new RuntimeException(e);
        } catch (InvalidKeySpecException e) {
            String msg = "Invalid key specification: " + e;
            Log.w(TAG, msg);
            throw new IOException(msg);
        }
    }

    /**
     * Verifies that the signature from the server matches the computed signature on the data.
     * Returns true if the data is correctly signed.
     *
     * @param publicKey  public key associated with the developer account
     * @param signedData signed data from server
     * @param signature  server signature
     * @return true if the data and signature match
     */
    static private Boolean verify(PublicKey publicKey, String signedData, String signature) {
        byte[] signatureBytes;
        try {
            signatureBytes = Base64.decode(signature, Base64.DEFAULT);
        } catch (IllegalArgumentException e) {
            Log.w(TAG, "Base64 decoding failed.");
            return false;
        }
        try {
            Signature signatureAlgorithm = Signature.getInstance(SIGNATURE_ALGORITHM);
            signatureAlgorithm.initVerify(publicKey);
            signatureAlgorithm.update(signedData.getBytes());
            if (!signatureAlgorithm.verify(signatureBytes)) {
                Log.w(TAG, "Signature verification failed...");
                return false;
            }
            return true;
        } catch (NoSuchAlgorithmException e) {
            // "RSA" is guaranteed to be available.
            throw new RuntimeException(e);
        } catch (InvalidKeyException e) {
            Log.e(TAG, "Invalid key specification.");
        } catch (SignatureException e) {
            Log.e(TAG, "Signature exception.");
        }
        return false;
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TrivialDriveKotlin/app/src/main/java/com/sample/android/trivialdrivesample/billing/Security.java [46:138]:
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class Security {
    static final private String TAG = "IABUtil/Security";
    static final private String KEY_FACTORY_ALGORITHM = "RSA";
    static final private String SIGNATURE_ALGORITHM = "SHA1withRSA";

    /**
     * BASE_64_ENCODED_PUBLIC_KEY should be YOUR APPLICATION PUBLIC KEY. You currently get this
     * from the Google Play developer console under the "Monetization Setup" category in the
     * Licensing area. This build has been setup so that if you define base64EncodedPublicKey in
     * your local.properties, it will be echoed into BuildConfig.
     */

    final private static String BASE_64_ENCODED_PUBLIC_KEY = BuildConfig.BASE64_ENCODED_PUBLIC_KEY;

    /**
     * Verifies that the data was signed with the given signature
     *
     * @param signedData the signed JSON string (signed, not encrypted)
     * @param signature  the signature for the data, signed with the private key
     */
    static public boolean verifyPurchase(String signedData, String signature) {
        if ((TextUtils.isEmpty(signedData) || TextUtils.isEmpty(BASE_64_ENCODED_PUBLIC_KEY)
                || TextUtils.isEmpty(signature))
        ) {
            Log.w(TAG, "Purchase verification failed: missing data.");
            return false;
        }
        try {
            PublicKey key = generatePublicKey(BASE_64_ENCODED_PUBLIC_KEY);
            return verify(key, signedData, signature);
        } catch (IOException e) {
            Log.e(TAG, "Error generating PublicKey from encoded key: " + e.getMessage());
            return false;
        }
    }

    /**
     * Generates a PublicKey instance from a string containing the Base64-encoded public key.
     *
     * @param encodedPublicKey Base64-encoded public key
     * @throws IOException if encoding algorithm is not supported or key specification
     *                     is invalid
     */
    static private PublicKey generatePublicKey(String encodedPublicKey) throws IOException {
        try {
            byte[] decodedKey = Base64.decode(encodedPublicKey, Base64.DEFAULT);
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_FACTORY_ALGORITHM);
            return keyFactory.generatePublic(new X509EncodedKeySpec(decodedKey));
        } catch (NoSuchAlgorithmException e) {
            // "RSA" is guaranteed to be available.
            throw new RuntimeException(e);
        } catch (InvalidKeySpecException e) {
            String msg = "Invalid key specification: " + e;
            Log.w(TAG, msg);
            throw new IOException(msg);
        }
    }

    /**
     * Verifies that the signature from the server matches the computed signature on the data.
     * Returns true if the data is correctly signed.
     *
     * @param publicKey  public key associated with the developer account
     * @param signedData signed data from server
     * @param signature  server signature
     * @return true if the data and signature match
     */
    static private Boolean verify(PublicKey publicKey, String signedData, String signature) {
        byte[] signatureBytes;
        try {
            signatureBytes = Base64.decode(signature, Base64.DEFAULT);
        } catch (IllegalArgumentException e) {
            Log.w(TAG, "Base64 decoding failed.");
            return false;
        }
        try {
            Signature signatureAlgorithm = Signature.getInstance(SIGNATURE_ALGORITHM);
            signatureAlgorithm.initVerify(publicKey);
            signatureAlgorithm.update(signedData.getBytes());
            if (!signatureAlgorithm.verify(signatureBytes)) {
                Log.w(TAG, "Signature verification failed...");
                return false;
            }
            return true;
        } catch (NoSuchAlgorithmException e) {
            // "RSA" is guaranteed to be available.
            throw new RuntimeException(e);
        } catch (InvalidKeyException e) {
            Log.e(TAG, "Invalid key specification.");
        } catch (SignatureException e) {
            Log.e(TAG, "Signature exception.");
        }
        return false;
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