Added in [API level 23](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

# Builder

*** ** * ** ***

Kotlin \|[Java](https://developer.android.com/reference/android/security/keystore/KeyProtection.Builder "View this page in Java")

```
class Builder
```

|---|---|
| [kotlin.Any](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html) ||
| ↳ | [android.security.keystore.KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) |

Builder of `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection` instances.

## Summary

| Public constructors ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#Builder(kotlin.Int)(purposes: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/index.html)` Creates a new instance of the `Builder`. |

| Public methods ||
|---|---|
| [KeyProtection](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#build()()` Builds an instance of `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection`. |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setBlockModes(kotlin.String)(vararg blockModes: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html!)` Sets the set of block modes (e.g., |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setDigests(kotlin.String)(vararg digests: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html!)` Sets the set of digest algorithms (e.g., |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setEncryptionPaddings(kotlin.String)(vararg paddings: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html!)` Sets the set of padding schemes (e.g., |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setInvalidatedByBiometricEnrollment(kotlin.Boolean)(invalidateKey: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html)` Sets whether this key should be invalidated on biometric enrollment. |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setIsStrongBoxBacked(kotlin.Boolean)(isStrongBoxBacked: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html)` Sets whether this key should be protected by a StrongBox security chip. |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setKeyValidityEnd(java.util.Date)(endDate: https://developer.android.com/reference/kotlin/java/util/Date.html#!)` Sets the time instant after which the key is no longer valid. |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setKeyValidityForConsumptionEnd(java.util.Date)(endDate: https://developer.android.com/reference/kotlin/java/util/Date.html#!)` Sets the time instant after which the key is no longer valid for decryption and verification. |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setKeyValidityForOriginationEnd(java.util.Date)(endDate: https://developer.android.com/reference/kotlin/java/util/Date.html#!)` Sets the time instant after which the key is no longer valid for encryption and signing. |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setKeyValidityStart(java.util.Date)(startDate: https://developer.android.com/reference/kotlin/java/util/Date.html#!)` Sets the time instant before which the key is not yet valid. |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setMaxUsageCount(kotlin.Int)(maxUsageCount: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/index.html)` Sets the maximum number of times the key is allowed to be used. |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setMgf1Digests(kotlin.String)(vararg mgf1Digests: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html!)` Sets the set of hash functions (e.g., |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setRandomizedEncryptionRequired(kotlin.Boolean)(required: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html)` Sets whether encryption using this key must be sufficiently randomized to produce different ciphertexts for the same plaintext every time. |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setSignaturePaddings(kotlin.String)(vararg paddings: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html!)` Sets the set of padding schemes (e.g., |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUnlockedDeviceRequired(kotlin.Boolean)(unlockedDeviceRequired: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html)` Sets whether this key is authorized to be used only while the device is unlocked. |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationParameters(kotlin.Int,%20kotlin.Int)(timeout: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/index.html, type: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/index.html)` Sets the duration of time (seconds) and authorization type for which this key is authorized to be used after the user is successfully authenticated. |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationRequired(kotlin.Boolean)(required: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html)` Sets whether this key is authorized to be used only if the user has been authenticated. |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationValidWhileOnBody(kotlin.Boolean)(remainsValid: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html)` Sets whether the key will remain authorized only until the device is removed from the user's body up to the limit of the authentication validity period (see `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationValidityDurationSeconds(kotlin.Int)` and `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationRequired(kotlin.Boolean)`). |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationValidityDurationSeconds(kotlin.Int)(seconds: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/index.html)` Sets the duration of time (seconds) for which this key is authorized to be used after the user is successfully authenticated. |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserConfirmationRequired(kotlin.Boolean)(required: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html)` Sets whether this key is authorized to be used only for messages confirmed by the user. |
| [KeyProtection.Builder](https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#) | `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserPresenceRequired(kotlin.Boolean)(required: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html)` Sets whether a test of user presence is required to be performed between the `Signature.initSign()` and `Signature.sign()` method calls. |

## Public constructors

### Builder

Added in [API level 23](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
Builder(purposes: Int)
```

Creates a new instance of the `Builder`.

| Parameters ||
|---|---|
| `purposes` | [Int](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/index.html): set of purposes (e.g., encrypt, decrypt, sign) for which the key can be used. Attempts to use the key for any other purpose will be rejected. See `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties`.`PURPOSE` flags. Value is either `0` or a combination of the following: - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#PURPOSE_ENCRYPT:kotlin.Int` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#PURPOSE_DECRYPT:kotlin.Int` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#PURPOSE_SIGN:kotlin.Int` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#PURPOSE_VERIFY:kotlin.Int` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#PURPOSE_WRAP_KEY:kotlin.Int` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#PURPOSE_AGREE_KEY:kotlin.Int` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#PURPOSE_ATTEST_KEY:kotlin.Int` |

## Public methods

### build

Added in [API level 23](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun build(): KeyProtection
```

Builds an instance of `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection`.

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection` | This value cannot be `null`. |

| Exceptions ||
|---|---|
| `java.lang.IllegalArgumentException` | if a required field is missing |

### setBlockModes

Added in [API level 23](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setBlockModes(vararg blockModes: String!): KeyProtection.Builder
```

Sets the set of block modes (e.g., `GCM`, `CBC`) with which the key can be used when encrypting/decrypting. Attempts to use the key with any other block modes will be rejected.

This must be specified for symmetric encryption/decryption keys.

See `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties`.`BLOCK_MODE` constants.

| Parameters ||
|---|---|
| `blockModes` | [String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html)!: Value is one of the following: - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#BLOCK_MODE_ECB:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#BLOCK_MODE_CBC:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#BLOCK_MODE_CTR:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#BLOCK_MODE_GCM:kotlin.String` |

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

### setDigests

Added in [API level 23](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setDigests(vararg digests: String!): KeyProtection.Builder
```

Sets the set of digest algorithms (e.g., `SHA-256`, `SHA-384`) with which the key can be used. Attempts to use the key with any other digest algorithm will be rejected.

This must be specified for signing/verification keys and RSA encryption/decryption keys used with RSA OAEP padding scheme because these operations involve a digest. For HMAC keys, the default is the digest specified in `https://developer.android.com/reference/kotlin/java/security/Key.html#getAlgorithm()` (e.g., `SHA-256` for key algorithm `HmacSHA256`). HMAC keys cannot be authorized for more than one digest.

For private keys used for TLS/SSL client or server authentication it is usually necessary to authorize the use of no digest (`https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#DIGEST_NONE:kotlin.String`). This is because TLS/SSL stacks typically generate the necessary digest(s) themselves and then use a private key to sign it.

See `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties`.`DIGEST` constants.

| Parameters ||
|---|---|
| `digests` | [String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html)!: Value is one of the following: - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#DIGEST_NONE:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#DIGEST_MD5:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#DIGEST_SHA1:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#DIGEST_SHA224:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#DIGEST_SHA256:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#DIGEST_SHA384:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#DIGEST_SHA512:kotlin.String` |

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

### setEncryptionPaddings

Added in [API level 23](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setEncryptionPaddings(vararg paddings: String!): KeyProtection.Builder
```

Sets the set of padding schemes (e.g., `OAEPPadding`, `PKCS7Padding`, `NoPadding`) with which the key can be used when encrypting/decrypting. Attempts to use the key with any other padding scheme will be rejected.

This must be specified for keys which are used for encryption/decryption.

For RSA private keys used by TLS/SSL servers to authenticate themselves to clients it is usually necessary to authorize the use of no/any padding (`https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#ENCRYPTION_PADDING_NONE:kotlin.String`) and/or PKCS#1 encryption padding (`https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#ENCRYPTION_PADDING_RSA_PKCS1:kotlin.String`). This is because RSA decryption is required by some cipher suites, and some stacks request decryption using no padding whereas others request PKCS#1 padding.

See `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties`.`ENCRYPTION_PADDING` constants.

| Parameters ||
|---|---|
| `paddings` | [String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html)!: Value is one of the following: - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#ENCRYPTION_PADDING_NONE:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#ENCRYPTION_PADDING_PKCS7:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#ENCRYPTION_PADDING_RSA_PKCS1:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#ENCRYPTION_PADDING_RSA_OAEP:kotlin.String` |

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

### setInvalidatedByBiometricEnrollment

Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setInvalidatedByBiometricEnrollment(invalidateKey: Boolean): KeyProtection.Builder
```

Sets whether this key should be invalidated on biometric enrollment. This applies only to keys which require user authentication (see `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationRequired(kotlin.Boolean)`) and if no positive validity duration has been set (see `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationValidityDurationSeconds(kotlin.Int)`, meaning the key is valid for biometric authentication only.

By default, `invalidateKey` is `true`, so keys that are valid for biometric authentication only are *irreversibly invalidated* when a new biometric is enrolled, or when all existing biometrics are deleted. That may be changed by calling this method with `invalidateKey` set to `false`.

Invalidating keys on enrollment of a new biometric or unenrollment of all biometrics improves security by ensuring that an unauthorized person who obtains the password can't gain the use of biometric-authenticated keys by enrolling their own biometric. However, invalidating keys makes key-dependent operations impossible, requiring some fallback procedure to authenticate the user and set up a new key.

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

### setIsStrongBoxBacked

Added in [API level 31](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setIsStrongBoxBacked(isStrongBoxBacked: Boolean): KeyProtection.Builder
```

Sets whether this key should be protected by a StrongBox security chip.

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

### setKeyValidityEnd

Added in [API level 23](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setKeyValidityEnd(endDate: Date!): KeyProtection.Builder
```

Sets the time instant after which the key is no longer valid.

By default, the key is valid at any instant.

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

**See Also**

- `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setKeyValidityStart(java.util.Date)`
- `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setKeyValidityForConsumptionEnd(java.util.Date)`
- `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setKeyValidityForOriginationEnd(java.util.Date)`

### setKeyValidityForConsumptionEnd

Added in [API level 23](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setKeyValidityForConsumptionEnd(endDate: Date!): KeyProtection.Builder
```

Sets the time instant after which the key is no longer valid for decryption and verification.

By default, the key is valid at any instant.

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

**See Also**

- `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setKeyValidityForOriginationEnd(java.util.Date)`

### setKeyValidityForOriginationEnd

Added in [API level 23](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setKeyValidityForOriginationEnd(endDate: Date!): KeyProtection.Builder
```

Sets the time instant after which the key is no longer valid for encryption and signing.

By default, the key is valid at any instant.

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

**See Also**

- `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setKeyValidityForConsumptionEnd(java.util.Date)`

### setKeyValidityStart

Added in [API level 23](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setKeyValidityStart(startDate: Date!): KeyProtection.Builder
```

Sets the time instant before which the key is not yet valid.

By default, the key is valid at any instant.

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

**See Also**

- `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setKeyValidityEnd(java.util.Date)`

### setMaxUsageCount

Added in [API level 31](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setMaxUsageCount(maxUsageCount: Int): KeyProtection.Builder
```

Sets the maximum number of times the key is allowed to be used. After every use of the key, the use counter will decrease. This authorization applies only to secret key and private key operations. Public key operations are not restricted. For example, after successfully encrypting and decrypting data using methods such as `https://developer.android.com/reference/kotlin/javax/crypto/Cipher.html#doFinal()`, the use counter of the secret key will decrease. After successfully signing data using methods such as `https://developer.android.com/reference/kotlin/java/security/Signature.html#sign()`, the use counter of the private key will decrease. When the use counter is depleted, the key will be marked for deletion by Android Keystore and any subsequent attempt to use the key will throw `https://developer.android.com/reference/kotlin/android/security/keystore/KeyPermanentlyInvalidatedException`. There is no key to be loaded from the Android Keystore once the exhausted key is permanently deleted, as if the key never existed before.

By default, there is no restriction on the usage of key.

Some secure hardware may not support this feature at all, in which case it will be enforced in software, some secure hardware may support it but only with maxUsageCount = 1, and some secure hardware may support it with larger value of maxUsageCount.

The PackageManger feature flags: `https://developer.android.com/reference/kotlin/android/content/pm/PackageManager.html#FEATURE_KEYSTORE_SINGLE_USE_KEY:kotlin.String` and `https://developer.android.com/reference/kotlin/android/content/pm/PackageManager.html#FEATURE_KEYSTORE_LIMITED_USE_KEY:kotlin.String` can be used to check whether the secure hardware cannot enforce this feature, can only enforce it with maxUsageCount = 1, or can enforce it with larger value of maxUsageCount.

| Parameters ||
|---|---|
| `maxUsageCount` | [Int](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/index.html): maximum number of times the key is allowed to be used or `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#UNRESTRICTED_USAGE_COUNT:kotlin.Int` if there is no restriction on the usage. |

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

### setMgf1Digests

Added in [API level 35](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setMgf1Digests(vararg mgf1Digests: String!): KeyProtection.Builder
```

Sets the set of hash functions (e.g., `SHA-256`, `SHA-384`) which could be used by the mask generation function MGF1 (which is used for certain operations with the key). Attempts to use the key with any other digest for the mask generation function will be rejected.

This can only be specified for signing/verification keys and RSA encryption/decryption keys used with RSA OAEP padding scheme because these operations involve a mask generation function (MGF1) with a digest. The default digest for MGF1 is `SHA-1`, which will be specified during key import time if no digests have been explicitly provided. When using the key, the caller may not specify any digests that were not provided during key import time. The caller may specify the default digest, `SHA-1`, if no digests were explicitly provided during key import (but it is not necessary to do so).

See `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties`.`DIGEST` constants.

| Parameters ||
|---|---|
| `mgf1Digests` | [String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html)!: This value may be `null`. Value is one of the following: - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#DIGEST_NONE:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#DIGEST_MD5:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#DIGEST_SHA1:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#DIGEST_SHA224:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#DIGEST_SHA256:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#DIGEST_SHA384:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#DIGEST_SHA512:kotlin.String` |

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

### setRandomizedEncryptionRequired

Added in [API level 23](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setRandomizedEncryptionRequired(required: Boolean): KeyProtection.Builder
```

Sets whether encryption using this key must be sufficiently randomized to produce different ciphertexts for the same plaintext every time. The formal cryptographic property being required is *indistinguishability under chosen-plaintext attack (`IND-CPA`)*. This property is important because it mitigates several classes of weaknesses due to which ciphertext may leak information about plaintext. For example, if a given plaintext always produces the same ciphertext, an attacker may see the repeated ciphertexts and be able to deduce something about the plaintext.

By default, `IND-CPA` is required.

When `IND-CPA` is required:

- transformation which do not offer `IND-CPA`, such as symmetric ciphers using `ECB` mode or RSA encryption without padding, are prohibited;
- in transformations which use an IV, such as symmetric ciphers in `GCM`, `CBC`, and `CTR` block modes, caller-provided IVs are rejected when encrypting, to ensure that only random IVs are used.
- Before disabling this requirement, consider the following approaches instead:
  - If you are generating a random IV for encryption and then initializing a Cipher using the IV, the solution is to let the `Cipher` generate a random IV instead. This will occur if the `Cipher` is initialized for encryption without an IV. The IV can then be queried via `https://developer.android.com/reference/kotlin/javax/crypto/Cipher.html#getIV()`.
  - If you are generating a non-random IV (e.g., an IV derived from something not fully random, such as the name of the file being encrypted, or transaction ID, or password, or a device identifier), consider changing your design to use a random IV which will then be provided in addition to the ciphertext to the entities which need to decrypt the ciphertext.
  - If you are using RSA encryption without padding, consider switching to padding schemes which offer `IND-CPA`, such as PKCS#1 or OAEP.

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

### setSignaturePaddings

Added in [API level 23](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setSignaturePaddings(vararg paddings: String!): KeyProtection.Builder
```

Sets the set of padding schemes (e.g., `PSS`, `PKCS#1`) with which the key can be used when signing/verifying. Attempts to use the key with any other padding scheme will be rejected.

This must be specified for RSA keys which are used for signing/verification.

See `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties`.`SIGNATURE_PADDING` constants.

| Parameters ||
|---|---|
| `paddings` | [String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html)!: Value is one of the following: - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#SIGNATURE_PADDING_RSA_PKCS1:kotlin.String` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#SIGNATURE_PADDING_RSA_PSS:kotlin.String` |

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

### setUnlockedDeviceRequired

Added in [API level 28](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setUnlockedDeviceRequired(unlockedDeviceRequired: Boolean): KeyProtection.Builder
```

Sets whether this key is authorized to be used only while the device is unlocked.

The device is considered to be locked for a user when the user's apps are currently inaccessible and some form of lock screen authentication is required to regain access to them. For the full definition, see `https://developer.android.com/reference/kotlin/android/app/KeyguardManager.html#isDeviceLocked()`.

Public key operations aren't restricted by `setUnlockedDeviceRequired(true)` and may be performed even while the device is locked. In Android 11 (API level 30) and lower, encryption and verification operations with symmetric keys weren't restricted either.

Keys that use `setUnlockedDeviceRequired(true)` can be imported and generated even while the device is locked, as long as the device has been unlocked at least once since the last reboot. However, such keys cannot be used (except for the unrestricted operations mentioned above) until the device is unlocked. Apps that need to encrypt data while the device is locked such that it can only be decrypted while the device is unlocked can generate a key and encrypt the data in software, import the key into Keystore using `setUnlockedDeviceRequired(true)`, and zeroize the original key.

`setUnlockedDeviceRequired(true)` is related to but distinct from `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationRequired(kotlin.Boolean)`. `setUnlockedDeviceRequired(true)` requires that the device be unlocked, whereas `setUserAuthenticationRequired(true)` requires that a specific type of strong authentication has happened within a specific time period. They may be used together or separately; there are cases in which one requirement can be satisfied but not the other.

**Warning:** Be careful using `setUnlockedDeviceRequired(true)` on Android 14 (API level 34) and lower, since the following bugs existed in Android 12 through 14:

- When the user didn't have a secure lock screen, unlocked-device-required keys couldn't be generated, imported, or used.
- When the user's secure lock screen was removed, all of that user's unlocked-device-required keys were automatically deleted.
- Unlocking the device with a non-strong biometric, such as face on many devices, didn't re-authorize the use of unlocked-device-required keys.
- Unlocking the device with a biometric didn't re-authorize the use of unlocked-device-required keys in profiles that share their parent user's lock.

These issues are fixed in Android 15, so apps can avoid them by using `setUnlockedDeviceRequired(true)` only on Android 15 and higher. Apps that use both `setUnlockedDeviceRequired(true)` and `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationRequired(kotlin.Boolean)` are unaffected by the first two issues, since the first two issues describe expected behavior for `setUserAuthenticationRequired(true)`.

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

### setUserAuthenticationParameters

Added in [API level 30](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setUserAuthenticationParameters(
    timeout: Int, 
    type: Int
): KeyProtection.Builder
```

Sets the duration of time (seconds) and authorization type for which this key is authorized to be used after the user is successfully authenticated. This has effect if the key requires user authentication for its use (see `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationRequired(kotlin.Boolean)`).

By default, if user authentication is required, it must take place for every use of the key.

These cryptographic operations will throw `https://developer.android.com/reference/kotlin/android/security/keystore/UserNotAuthenticatedException` during initialization if the user needs to be authenticated to proceed. This situation can be resolved by the user authenticating with the appropriate biometric or credential as required by the key. See `https://developer.android.com/reference/kotlin/android/hardware/biometrics/BiometricPrompt.Builder.html#setAllowedAuthenticators(kotlin.Int)` and `https://developer.android.com/reference/kotlin/android/hardware/biometrics/BiometricManager.Authenticators.html#`.

Once resolved, initializing a new cryptographic operation using this key (or any other key which is authorized to be used for a fixed duration of time after user authentication) should succeed provided the user authentication flow completed successfully.

| Parameters ||
|---|---|
| `timeout` | [Int](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/index.html): duration in seconds or `0` if user authentication must take place for every use of the key. Value is 0 or greater |
| `type` | [Int](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/index.html): set of authentication types which can authorize use of the key. See `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties`.`AUTH` flags. Value is either `0` or a combination of the following: - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#AUTH_BIOMETRIC_STRONG:kotlin.Int` - `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProperties#AUTH_DEVICE_CREDENTIAL:kotlin.Int` |

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

**See Also**

- `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationRequired(kotlin.Boolean)`
- `https://developer.android.com/reference/kotlin/android/hardware/biometrics/BiometricPrompt.html#`
- `https://developer.android.com/reference/kotlin/android/hardware/biometrics/BiometricPrompt.CryptoObject.html#`
- `https://developer.android.com/reference/kotlin/android/app/KeyguardManager.html#`

### setUserAuthenticationRequired

Added in [API level 23](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setUserAuthenticationRequired(required: Boolean): KeyProtection.Builder
```

Sets whether this key is authorized to be used only if the user has been authenticated.

By default, the key is authorized to be used regardless of whether the user has been authenticated.

When user authentication is required:

- The key can only be import if secure lock screen is set up (see `https://developer.android.com/reference/kotlin/android/app/KeyguardManager.html#isDeviceSecure()`). Additionally, if the key requires that user authentication takes place for every use of the key (see `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationValidityDurationSeconds(kotlin.Int)`), at least one biometric must be enrolled (see `https://developer.android.com/reference/kotlin/android/hardware/biometrics/BiometricManager.html#canAuthenticate()`).
- The use of the key must be authorized by the user by authenticating to this Android device using a subset of their secure lock screen credentials such as password/PIN/pattern or biometric. [More information](https://developer.android.com/training/articles/keystore.html#UserAuthentication).
- The key will become *irreversibly invalidated* once the secure lock screen is disabled (reconfigured to None, Swipe or other mode which does not authenticate the user) or when the secure lock screen is forcibly reset (e.g., by a Device Administrator). Additionally, if the key requires that user authentication takes place for every use of the key, it is also irreversibly invalidated once a new biometric is enrolled or once no more biometrics are enrolled, unless `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setInvalidatedByBiometricEnrollment(kotlin.Boolean)` is used to allow validity after enrollment. Attempts to initialize cryptographic operations using such keys will throw `https://developer.android.com/reference/kotlin/android/security/keystore/KeyPermanentlyInvalidatedException`.

This authorization applies only to secret key and private key operations. Public key operations are not restricted.

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

**See Also**

- `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationValidityDurationSeconds(kotlin.Int)`
- `https://developer.android.com/reference/kotlin/android/app/KeyguardManager.html#isDeviceSecure()`
- `https://developer.android.com/reference/kotlin/android/hardware/biometrics/BiometricManager.html#canAuthenticate()`

### setUserAuthenticationValidWhileOnBody

Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setUserAuthenticationValidWhileOnBody(remainsValid: Boolean): KeyProtection.Builder
```

Sets whether the key will remain authorized only until the device is removed from the user's body up to the limit of the authentication validity period (see `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationValidityDurationSeconds(kotlin.Int)` and `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationRequired(kotlin.Boolean)`). Once the device has been removed from the user's body, the key will be considered unauthorized and the user will need to re-authenticate to use it. If the device does not have an on-body sensor or the key does not have an authentication validity period, this parameter has no effect.

Since Android 12 (API level 31), this parameter has no effect even on devices that have an on-body sensor. A future version of Android may restore enforcement of this parameter. Meanwhile, it is recommended to not use it.

| Parameters ||
|---|---|
| `remainsValid` | [Boolean](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html): if `true`, and if the device supports enforcement of this parameter, the key will be invalidated when the device is removed from the user's body or when the authentication validity expires, whichever occurs first. |

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

### setUserAuthenticationValidityDurationSeconds

Added in [API level 23](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)  
Deprecated in [API level 30](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setUserAuthenticationValidityDurationSeconds(seconds: Int): KeyProtection.Builder
```

**Deprecated:** *See `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationParameters(kotlin.Int,%20kotlin.Int)`*

Sets the duration of time (seconds) for which this key is authorized to be used after the user is successfully authenticated. This has effect if the key requires user authentication for its use (see `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationRequired(kotlin.Boolean)`).

By default, if user authentication is required, it must take place for every use of the key.

Cryptographic operations involving keys which require user authentication to take place for every operation can only use biometric authentication. This is achieved by initializing a cryptographic operation (`https://developer.android.com/reference/kotlin/java/security/Signature.html#`, `https://developer.android.com/reference/kotlin/javax/crypto/Cipher.html#`, `https://developer.android.com/reference/kotlin/javax/crypto/Mac.html#`) with the key, wrapping it into a `https://developer.android.com/reference/kotlin/android/hardware/biometrics/BiometricPrompt.CryptoObject.html#`, invoking `BiometricPrompt.authenticate` with `CryptoObject`, and proceeding with the cryptographic operation only if the authentication flow succeeds.

Cryptographic operations involving keys which are authorized to be used for a duration of time after a successful user authentication event can only use secure lock screen authentication. These cryptographic operations will throw `https://developer.android.com/reference/kotlin/android/security/keystore/UserNotAuthenticatedException` during initialization if the user needs to be authenticated to proceed. This situation can be resolved by the user unlocking the secure lock screen of the Android or by going through the confirm credential flow initiated by `https://developer.android.com/reference/kotlin/android/app/KeyguardManager.html#createConfirmDeviceCredentialIntent(kotlin.CharSequence,%20kotlin.CharSequence)`. Once resolved, initializing a new cryptographic operation using this key (or any other key which is authorized to be used for a fixed duration of time after user authentication) should succeed provided the user authentication flow completed successfully.

| Parameters ||
|---|---|
| `seconds` | [Int](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/index.html): duration in seconds or `-1` if user authentication must take place for every use of the key. Value is -1 or greater |

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

**See Also**

- `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationRequired(kotlin.Boolean)`
- `https://developer.android.com/reference/kotlin/android/hardware/biometrics/BiometricPrompt.html#`
- `https://developer.android.com/reference/kotlin/android/hardware/biometrics/BiometricPrompt.CryptoObject.html#`
- `https://developer.android.com/reference/kotlin/android/app/KeyguardManager.html#`

### setUserConfirmationRequired

Added in [API level 28](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setUserConfirmationRequired(required: Boolean): KeyProtection.Builder
```

Sets whether this key is authorized to be used only for messages confirmed by the user. Confirmation is separate from user authentication (see `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#setUserAuthenticationRequired(kotlin.Boolean)`). Keys can be created that require confirmation but not user authentication, or user authentication but not confirmation, or both. Confirmation verifies that some user with physical possession of the device has approved a displayed message. User authentication verifies that the correct user is present and has authenticated.

This authorization applies only to secret key and private key operations. Public key operations are not restricted. See `https://developer.android.com/reference/kotlin/android/security/ConfirmationPrompt.html#` class for more details about user confirmations.

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |

### setUserPresenceRequired

Added in [API level 28](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)

```
fun setUserPresenceRequired(required: Boolean): KeyProtection.Builder
```

Sets whether a test of user presence is required to be performed between the `Signature.initSign()` and `Signature.sign()` method calls. It requires that the KeyStore implementation have a direct way to validate the user presence for example a KeyStore hardware backed strongbox can use a button press that is observable in hardware. A test for user presence is tangential to authentication. The test can be part of an authentication step as long as this step can be validated by the hardware protecting the key and cannot be spoofed. For example, a physical button press can be used as a test of user presence if the other pins connected to the button are not able to simulate a button press. There must be no way for the primary processor to fake a button press, or that button must not be used as a test of user presence.

| Return ||
|---|---|
| `https://developer.android.com/reference/kotlin/android/security/keystore/KeyProtection.Builder#` | This value cannot be `null`. |