Kotlin conversion: KeyRingProtectionSettings

pgpainless-core/src/main/kotlin/org/pgpainless/key/protection/KeyRingProtectionSettings.kt

@@ -0,0 +1,56 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.key.protection
+
+import org.pgpainless.algorithm.HashAlgorithm
+import org.pgpainless.algorithm.SymmetricKeyAlgorithm
+
+/**
+ * Secret key protection settings for iterated and salted S2K.
+ * The salt gets randomly chosen by the library each time.
+ * Note, that the s2kCount is the already encoded single-octet number.
+ *
+ * @see <a href="https://www.rfc-editor.org/rfc/rfc4880#section-3.7.1.3">Encoding Formula</a>
+ *
+ * @param encryptionAlgorithm encryption algorithm
+ * @param hashAlgorithm hash algorithm
+ * @param s2kCount encoded (!) s2k iteration count
+ */
+data class KeyRingProtectionSettings(
+        val encryptionAlgorithm: SymmetricKeyAlgorithm,
+        val hashAlgorithm: HashAlgorithm,
+        val s2kCount: Int
+) {
+
+    /**
+     * Create a [KeyRingProtectionSettings] object using the given encryption algorithm, [HashAlgorithm.SHA1] and
+     * 65536 iterations.
+     * It is okay to use SHA1 here, since we don't care about collisions.
+     *
+     * @param encryptionAlgorithm encryption algorithm
+     */
+    constructor(encryptionAlgorithm: SymmetricKeyAlgorithm): this(encryptionAlgorithm, HashAlgorithm.SHA1, 0x60)
+
+    init {
+        require(encryptionAlgorithm != SymmetricKeyAlgorithm.NULL) {
+            "Unencrypted is not allowed here!"
+        }
+        require(s2kCount > 0) {
+            "s2kCount cannot be less than 1."
+        }
+    }
+
+    companion object {
+
+        /**
+         * Secure default settings using [SymmetricKeyAlgorithm.AES_256], [HashAlgorithm.SHA256]
+         * and an iteration count of 65536.
+         *
+         * @return secure protection settings
+         */
+        @JvmStatic
+        fun secureDefaultSettings() = KeyRingProtectionSettings(SymmetricKeyAlgorithm.AES_256, HashAlgorithm.SHA256, 0x60)
+    }
+}