1 files changed, 31 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/crypto/SkippingCipher.java b/core/src/main/java/org/spongycastle/crypto/SkippingCipher.java
new file mode 100644
index 00000000..653182cd
--- /dev/null
+++ b/core/src/main/java/org/spongycastle/crypto/SkippingCipher.java
@@ -0,0 +1,31 @@
+package org.spongycastle.crypto;
+
+/**
+ * Ciphers producing a key stream which can be reset to particular points in the stream implement this.
+ */
+public interface SkippingCipher
+{
+    /**
+     * Skip numberOfBytes forwards, or backwards.
+     *
+     * @param numberOfBytes the number of bytes to skip (positive forward, negative backwards).
+     * @return the number of bytes actually skipped.
+     * @throws java.lang.IllegalArgumentException if numberOfBytes is an invalid value.
+     */
+    long skip(long numberOfBytes);
+
+    /**
+     * Reset the cipher and then skip forward to a given position.
+     *
+     * @param position the number of bytes in to set the cipher state to.
+     * @return the byte position moved to.
+     */
+    long seekTo(long position);
+
+    /**
+     * Return the current "position" of the cipher
+     *
+     * @return the current byte position.
+     */
+    long getPosition();
+}