1 files changed, 117 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/pqc/crypto/DigestingMessageSigner.java b/core/src/main/java/org/spongycastle/pqc/crypto/DigestingMessageSigner.java
new file mode 100644
index 00000000..b58a5278
--- /dev/null
+++ b/core/src/main/java/org/spongycastle/pqc/crypto/DigestingMessageSigner.java
@@ -0,0 +1,117 @@
+package org.spongycastle.pqc.crypto;
+
+import org.spongycastle.crypto.CipherParameters;
+import org.spongycastle.crypto.Digest;
+import org.spongycastle.crypto.Signer;
+import org.spongycastle.crypto.params.AsymmetricKeyParameter;
+import org.spongycastle.crypto.params.ParametersWithRandom;
+
+
+/**
+ * Implements the sign and verify functions for a Signature Scheme which can use a hash function.
+ */
+public class DigestingMessageSigner
+    implements Signer
+{
+    private final Digest messDigest;
+    private final MessageSigner messSigner;
+    private boolean forSigning;
+
+    public DigestingMessageSigner(MessageSigner messSigner, Digest messDigest)
+    {
+        this.messSigner = messSigner;
+        this.messDigest = messDigest;
+    }
+
+    public void init(boolean forSigning,
+                     CipherParameters param)
+    {
+
+        this.forSigning = forSigning;
+        AsymmetricKeyParameter k;
+
+        if (param instanceof ParametersWithRandom)
+        {
+            k = (AsymmetricKeyParameter)((ParametersWithRandom)param).getParameters();
+        }
+        else
+        {
+            k = (AsymmetricKeyParameter)param;
+        }
+
+        if (forSigning && !k.isPrivate())
+        {
+            throw new IllegalArgumentException("Signing Requires Private Key.");
+        }
+
+        if (!forSigning && k.isPrivate())
+        {
+            throw new IllegalArgumentException("Verification Requires Public Key.");
+        }
+
+        reset();
+
+        messSigner.init(forSigning, param);
+    }
+
+
+    /**
+     * This function signs the message that has been updated, making use of the
+     * private key.
+     *
+     * @return the signature of the message.
+     */
+    public byte[] generateSignature()
+    {
+        if (!forSigning)
+        {
+            throw new IllegalStateException("RainbowDigestSigner not initialised for signature generation.");
+        }
+
+        byte[] hash = new byte[messDigest.getDigestSize()];
+        messDigest.doFinal(hash, 0);
+
+        return messSigner.generateSignature(hash);
+    }
+
+    /**
+     * This function verifies the signature of the message that has been
+     * updated, with the aid of the public key.
+     *
+     * @param signature the signature of the message is given as a byte array.
+     * @return true if the signature has been verified, false otherwise.
+     */
+    public boolean verify(byte[] signature)
+    {
+        if (forSigning)
+        {
+            throw new IllegalStateException("RainbowDigestSigner not initialised for verification");
+        }
+
+        byte[] hash = new byte[messDigest.getDigestSize()];
+        messDigest.doFinal(hash, 0);
+
+        return messSigner.verifySignature(hash, signature);
+
+    }
+
+    public void update(byte b)
+    {
+        messDigest.update(b);
+    }
+
+    public void update(byte[] in, int off, int len)
+    {
+        messDigest.update(in, off, len);
+    }
+
+    public void reset()
+    {
+        messDigest.reset();
+    }
+
+    public boolean verifySignature(byte[] signature)
+    {
+        return this.verify(signature);
+    }
+}