Crypto: add a small cryptography library module with CipherFactory

libraries/cryptography/api/build.gradle.kts

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+plugins {
+    id("io.element.android-library")
+}
+
+android {
+    namespace = "io.element.android.libraries.cryptography.api"
+}

libraries/cryptography/api/src/main/kotlin/io/element/android/libraries/cryptography/api/CipherFactory.kt

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+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.element.android.libraries.cryptography.api
+
+import javax.crypto.Cipher
+
+/**
+ * Factory to create [Cipher] instances for encryption and decryption.
+ * The implementation should use a secure way to store the keys.
+ */
+interface CipherFactory {
+    /**
+     * Create a [Cipher] instance for encryption.
+     * @param alias the alias of the key used for encryption.
+     * @return the [Cipher] instance.
+     */
+    fun createEncryptionCipher(alias: String): Cipher
+
+    /**
+     * Create a [Cipher] instance for decryption.
+     * @param alias the alias of the key used for encryption.
+     * @param initializationVector the initialization vector used for encryption.
+     * @return the [Cipher] instance.
+     */
+    fun createDecryptionCipher(alias: String, initializationVector: ByteArray): Cipher
+}