1 files changed, 26 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/crypto/BasicAgreement.java b/core/src/main/java/org/spongycastle/crypto/BasicAgreement.java
new file mode 100644
index 00000000..e6e003c6
--- /dev/null
+++ b/core/src/main/java/org/spongycastle/crypto/BasicAgreement.java
@@ -0,0 +1,26 @@
+package org.spongycastle.crypto;
+
+import java.math.BigInteger;
+
+/**
+ * The basic interface that basic Diffie-Hellman implementations
+ * conforms to.
+ */
+public interface BasicAgreement
+{
+    /**
+     * initialise the agreement engine.
+     */
+    void init(CipherParameters param);
+
+    /**
+     * return the field size for the agreement algorithm in bytes.
+     */
+    int getFieldSize();
+
+    /**
+     * given a public key from a given party calculate the next
+     * message in the agreement sequence. 
+     */
+    BigInteger calculateAgreement(CipherParameters pubKey);
+}