1 files changed, 123 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/crypto/params/HKDFParameters.java b/core/src/main/java/org/spongycastle/crypto/params/HKDFParameters.java
new file mode 100644
index 00000000..94595a15
--- /dev/null
+++ b/core/src/main/java/org/spongycastle/crypto/params/HKDFParameters.java
@@ -0,0 +1,123 @@
+package org.spongycastle.crypto.params;
+
+import org.spongycastle.crypto.DerivationParameters;
+import org.spongycastle.util.Arrays;
+
+/**
+ * Parameter class for the HKDFBytesGenerator class.
+ */
+public class HKDFParameters
+    implements DerivationParameters
+{
+    private final byte[] ikm;
+    private final boolean skipExpand;
+    private final byte[] salt;
+    private final byte[] info;
+
+    private HKDFParameters(final byte[] ikm, final boolean skip,
+                           final byte[] salt, final byte[] info)
+    {
+        if (ikm == null)
+        {
+            throw new IllegalArgumentException(
+                "IKM (input keying material) should not be null");
+        }
+
+        this.ikm = Arrays.clone(ikm);
+
+        this.skipExpand = skip;
+
+        if (salt == null || salt.length == 0)
+        {
+            this.salt = null;
+        }
+        else
+        {
+            this.salt = Arrays.clone(salt);
+        }
+
+        if (info == null)
+        {
+            this.info = new byte[0];
+        }
+        else
+        {
+            this.info = Arrays.clone(info);
+        }
+    }
+
+    /**
+     * Generates parameters for HKDF, specifying both the optional salt and
+     * optional info. Step 1: Extract won't be skipped.
+     *
+     * @param ikm  the input keying material or seed
+     * @param salt the salt to use, may be null for a salt for hashLen zeros
+     * @param info the info to use, may be null for an info field of zero bytes
+     */
+    public HKDFParameters(final byte[] ikm, final byte[] salt, final byte[] info)
+    {
+        this(ikm, false, salt, info);
+    }
+
+    /**
+     * Factory method that makes the HKDF skip the extract part of the key
+     * derivation function.
+     *
+     * @param ikm  the input keying material or seed, directly used for step 2:
+     *             Expand
+     * @param info the info to use, may be null for an info field of zero bytes
+     * @return HKDFParameters that makes the implementation skip step 1
+     */
+    public static HKDFParameters skipExtractParameters(final byte[] ikm,
+                                                       final byte[] info)
+    {
+
+        return new HKDFParameters(ikm, true, null, info);
+    }
+
+    public static HKDFParameters defaultParameters(final byte[] ikm)
+    {
+        return new HKDFParameters(ikm, false, null, null);
+    }
+
+    /**
+     * Returns the input keying material or seed.
+     *
+     * @return the keying material
+     */
+    public byte[] getIKM()
+    {
+        return Arrays.clone(ikm);
+    }
+
+    /**
+     * Returns if step 1: extract has to be skipped or not
+     *
+     * @return true for skipping, false for no skipping of step 1
+     */
+    public boolean skipExtract()
+    {
+        return skipExpand;
+    }
+
+    /**
+     * Returns the salt, or null if the salt should be generated as a byte array
+     * of HashLen zeros.
+     *
+     * @return the salt, or null
+     */
+    public byte[] getSalt()
+    {
+        return Arrays.clone(salt);
+    }
+
+    /**
+     * Returns the info field, which may be empty (null is converted to empty).
+     *
+     * @return the info field, never null
+     */
+    public byte[] getInfo()
+    {
+        return Arrays.clone(info);
+    }
+}