# Master License for Android

Master license is the offline license that allows using Mobile SDKs with any `bundle_id`, unlike the regular licenses. To get a master license, create a pair of keys as shown below. Email us the public key, and we will email you the master license shortly after that.\
Your application needs to sign its `bundle_id` with the private key, and the Mobile SDK checks the signature using the public key from the master license. Master licenses are time-limited.

## Generating Keys

This section describes the process of creating your private and public keys.

### Creating a Private Key

To create a private key, run the commands below one by one.

```bash
openssl genpkey -algorithm RSA -outform DER -out privateKey.der -pkeyopt rsa_keygen_bits:2048
# for MacOS
base64 -i privateKey.der -o privateKey.txt
# for Linux 
base64 -w 0 privateKey.der > privateKey.txt
```

You will get these files:

* *privateKey.der* is a private .der key;
* *privateKey.txt* is *privateKey.der* encoded by *base64*. This key containing will be used as the host app *bundle\_id* signature.

The OpenSSL command specification: <https://www.openssl.org/docs/man1.1.1/man1/openssl-pkcs8.html>

### Creating a Public Key

To create a public key, run this command.

```sh
openssl rsa -pubout -in privateKey.der -out publicKey.pub
```

You will get the public key file: *publicKey.pub*. To get a license, please email us this file. We will email you the license.

## SDK Integration

SDK initialization:

```kotlin
fun init(
    context: Context,
    licenseSources: List<LicenseSource>,
    masterLicenseSignature: String,
    statusListener: StatusListener<LicensePayload>? = null,
)
```

{% hint style="info" %}
For Android 6.0 (API level 23) and older:

1. Add the `implementation 'com.madgag.spongycastle:prov:1.58.0.0'` dependency;
2. Before creating a signature, call `Security.insertProviderAt(org.spongycastle.jce.provider.BouncyCastleProvider(), 1)`
   {% endhint %}

Prior to the SDK initializing, create a base64-encoded signature for the host app `bundle_id` using the private key.

Signature creation example:

```kotlin
private fun getMasterSignature(): String {
    Security.insertProviderAt(org.spongycastle.jce.provider.BouncyCastleProvider(), 1)

    val privateKeyBase64String = "the string copied from the privateKey.txt file"
    // with key example:
    // val privateKeyBase64String = "MIIEpAIBAAKCAQEAxnpv02nNR34uNS0yLRK1o7Za2hs4Rr0s1V1/e1JZpCaK8o5/3uGV+qiaTbKqU6x1tTrlXwE2BRzZJLLQdTfBL/rzqVLQC/n+kAmvsqtHMTUqKquSybSTY/zAxqHF3Fk59Cqisr/KQamPh2tmg3Gu61rr9gU1rOglnuqt7FioNMCMvjW7ciPv+jiawLxaPrzNiApLqHVN+xCFh6LLb4YlGRaNUXlOgnoLGWSQEsLwBZFkDJDSLTJheNVn9oa3PXg4OIlJIPlYVKzIDDcSTNKdzM6opkS5d+86yjI1aTKEH3Zs64+QoEuoDfXUxS3TOUFx8P+wfjOR5tYAT+7TRN4ocwIDAQABAoIBAATWJPV05ZCxbXTURh29D/oOToZ0FVn78CS+44Vgy1hprAcfG9SVkK8L/r6X9PiXAkNJTR+Uivly64Oua8//bNC7f8aHgxRXojFmWwayj8iOMBncFnad1N2h4hy1AnpNHlFp3I8Yh1g0RpAZOOVJFucbTxaup9Ev0wLdWyGgQ3ENmRXAyLU5iUDwUSXg59RCBFKcmsMT2GmmJt1BU4P3lL9KVyLBktqeDWR/l5K5y8pPo6K7m9NaOkynpZo+mHVoOTCtmTj5TC/MH9YRHlF15VxQgBbZXuBPxlYoQCsMDEcZlMBWNw3cNR6VBmGiwHIc/tzSHZVsbY0VRCYEbxhCBZkCgYEA+Uz0VYKnIWViQF2Na6LFuqlfljZlkOvdpU4puYTCdlfpKNT3txYzO0T00HHY9YG9k1AW78YxQwsopOXDCmCqMoRqlbn1SBe6v49pVB85fPYU2+L+lftpPlx6Wa0xcgzwOBZonHb4kvp1tWhUH+B5t27gnvRz/rx5jV2EfmWinycCgYEAy8/aklZcgoXWf93N/0EZcfzQo90LfftkKonpzEyxSzqCw7B9fHY68q/j9HoP4xgJXUKbx1Fa8Wccc0DSoXsSiQFrLhnT8pE2s1ZWvPaUqyT5iOZOW6R+giFSLPWEdwm6+BeFoPQQFHf8XH3Z2QoAepPrEPiDoGN1GSIXcCwoe9UCgYEAgoKj4uQsJJKT1ghj0bZ79xVWQigmEbE47qI1u7Zhq1yoZkTfjcykc2HNHBaNszEBks45w7qo7WU5GOJjsdobH6kst0eLvfsWO9STGoPiL6YQE3EJQHFGjmwRbUL7AK7/Tw2EJG0wApn150s/xxRYBAyasPxegTwgEj6j7xu7/78CgYEAxbkI52zG5I0o0fWBcf9ayx2j30SDcJ3gx+/xlBRW74986pGeu48LkwMWV8fO/9YCx6nl7JC9dHI+xIT/kk8OZUGuFBRUbP95nLPHBB0Hj50YRDqBjCBh5qaizSEGeGFFNIfFSKddri3U8nnZTNiKLGCx7E3bjE7QfCh5qoX8ZF0CgYAtsEPTNKWZKA23qTFI+XAg/cVZpbSjvbHDSE8QB6X8iaKJFXbmIC0LV5tQO/KT4sK8g40m2N9JWUnaryTiXClaUGU3KnSlBdkIA+I77VvMKMGSg+uf4OdfJvvcs4hZTqZRdTm3dez8rsUdiW1cX/iI/dJxF4964YIFR65wL+SoRg=="
    val sig = Signature.getInstance("SHA512WithRSA")
    val keySpec = PKCS8EncodedKeySpec(Base64.decode(privateKeyBase64String, Base64.DEFAULT))
    val keyFactory = KeyFactory.getInstance("RSA")
    sig.initSign(keyFactory.generatePrivate(keySpec))
    sig.update(packageName.toByteArray(Charsets.UTF_8))
    return Base64.encodeToString(sig.sign(), Base64.DEFAULT).replace("\n", "")
}
```

Pass the signature as the `masterLicenseSignature` parameter during the SDK initialization.

If the signature is invalid, the initialization continues as usual: the SDK checks the list of `bundle_id` included into the license, like it does it by default without a master license.


---

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