1 files changed, 61 insertions, 0 deletions
diff --git a/src/main/java/org/whispersystems/libaxolotl/kdf/DerivedMessageSecrets.java b/src/main/java/org/whispersystems/libaxolotl/kdf/DerivedMessageSecrets.java
new file mode 100644
index 00000000..b3f54fb8
--- /dev/null
+++ b/src/main/java/org/whispersystems/libaxolotl/kdf/DerivedMessageSecrets.java
@@ -0,0 +1,61 @@
+/**
+ * Copyright (C) 2014 Open Whisper Systems
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.whispersystems.libaxolotl.kdf;
+
+import org.whispersystems.libaxolotl.util.ByteUtil;
+
+import java.text.ParseException;
+
+import javax.crypto.spec.IvParameterSpec;
+import javax.crypto.spec.SecretKeySpec;
+
+public class DerivedMessageSecrets {
+
+  public  static final int SIZE              = 80;
+  private static final int CIPHER_KEY_LENGTH = 32;
+  private static final int MAC_KEY_LENGTH    = 32;
+  private static final int IV_LENGTH         = 16;
+
+  private final SecretKeySpec   cipherKey;
+  private final SecretKeySpec   macKey;
+  private final IvParameterSpec iv;
+
+  public DerivedMessageSecrets(byte[] okm) {
+    try {
+      byte[][] keys = ByteUtil.split(okm, CIPHER_KEY_LENGTH, MAC_KEY_LENGTH, IV_LENGTH);
+
+      this.cipherKey = new SecretKeySpec(keys[0], "AES");
+      this.macKey    = new SecretKeySpec(keys[1], "HmacSHA256");
+      this.iv        = new IvParameterSpec(keys[2]);
+    } catch (ParseException e) {
+      throw new AssertionError(e);
+    }
+  }
+
+  public SecretKeySpec getCipherKey() {
+    return cipherKey;
+  }
+
+  public SecretKeySpec getMacKey() {
+    return macKey;
+  }
+
+  public IvParameterSpec getIv() {
+    return iv;
+  }
+}