1 files changed, 38 insertions, 0 deletions
diff --git a/java/src/main/java/org/whispersystems/libaxolotl/groups/ratchet/SenderMessageKey.java b/java/src/main/java/org/whispersystems/libaxolotl/groups/ratchet/SenderMessageKey.java
new file mode 100644
index 00000000..8808a8e8
--- /dev/null
+++ b/java/src/main/java/org/whispersystems/libaxolotl/groups/ratchet/SenderMessageKey.java
@@ -0,0 +1,38 @@
+package org.whispersystems.libaxolotl.groups.ratchet;
+
+import org.whispersystems.libaxolotl.kdf.HKDFv3;
+import org.whispersystems.libaxolotl.util.ByteUtil;
+
+public class SenderMessageKey {
+
+  private final int    iteration;
+  private final byte[] iv;
+  private final byte[] cipherKey;
+  private final byte[] seed;
+
+  public SenderMessageKey(int iteration, byte[] seed) {
+    byte[] derivative = new HKDFv3().deriveSecrets(seed, "WhisperGroup".getBytes(), 48);
+    byte[][] parts    = ByteUtil.split(derivative, 16, 32);
+
+    this.iteration = iteration;
+    this.seed      = seed;
+    this.iv        = parts[0];
+    this.cipherKey = parts[1];
+  }
+
+  public int getIteration() {
+    return iteration;
+  }
+
+  public byte[] getIv() {
+    return iv;
+  }
+
+  public byte[] getCipherKey() {
+    return cipherKey;
+  }
+
+  public byte[] getSeed() {
+    return seed;
+  }
+}