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diff --git a/security-utils/src/main/java/com/yahoo/security/HKDF.java b/security-utils/src/main/java/com/yahoo/security/HKDF.java
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+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.security;
+
+import javax.crypto.Mac;
+import javax.crypto.spec.SecretKeySpec;
+import java.nio.ByteBuffer;
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.util.Objects;
+
+/**
+ * Implementation of RFC-5869 HMAC-based Extract-and-Expand Key Derivation Function (HKDF).
+ *
+ * <p>The HKDF is initialized ("extracted") from a (non-secret) salt and a secret key.
+ * From this, any number of secret keys can be derived ("expanded") deterministically.</p>
+ *
+ * <p>When multiple keys are to be derived from the same initial keying/salting material,
+ * each separate key should use a distinct "context" in the {@link #expand(int, byte[])}
+ * call. This ensures that there exists a domain separation between the keys.
+ * Using the same context as another key on a HKDF initialized with the same salt+key
+ * results in the exact same derived key material as that key.</p>
+ *
+ * <p>This implementation only offers HMAC-SHA256-based key derivation.</p>
+ *
+ * @see <a href="https://tools.ietf.org/html/rfc5869">RFC-5869</a>
+ * @see <a href="https://en.wikipedia.org/wiki/HKDF">HKDF on Wikipedia</a>
+ *
+ * @author vekterli
+ */
+public class HKDF {
+
+    private static final int    HASH_LEN        = 32; // Fixed output size of HMAC-SHA256. Corresponds to HashLen in the spec
+    private static final byte[] EMPTY_BYTES     = new byte[0];
+    private static final byte[] ALL_ZEROS_SALT  = new byte[HASH_LEN];
+    public static final int     MAX_OUTPUT_SIZE = 255 * HASH_LEN;
+
+    private final byte[] pseudoRandomKey; // Corresponds to "PRK" in spec
+
+    private HKDF(byte[] pseudoRandomKey) {
+        this.pseudoRandomKey = pseudoRandomKey;
+    }
+
+    private static Mac createHmacSha256() {
+        try {
+            return Mac.getInstance("HmacSHA256");
+        } catch (NoSuchAlgorithmException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private static SecretKeySpec hmacKeyFrom(byte[] rawKey) {
+        return new SecretKeySpec(rawKey, "HmacSHA256");
+    }
+
+    private static Mac createKeyedHmacSha256(byte[] rawKey) {
+        var hmac = createHmacSha256();
+        try {
+            hmac.init(hmacKeyFrom(rawKey));
+        } catch (InvalidKeyException e) {
+            throw new RuntimeException(e);
+        }
+        return hmac;
+    }
+
+    private static void validateExtractionParams(byte[] salt, byte[] ikm) {
+        Objects.requireNonNull(salt);
+        Objects.requireNonNull(ikm);
+        if (ikm.length == 0) {
+            throw new IllegalArgumentException("HKDF extraction IKM array can not be empty");
+        }
+        if (salt.length == 0) {
+            throw new IllegalArgumentException("HKDF extraction salt array can not be empty");
+        }
+    }
+
+    /**
+     * Creates and returns a new HKDF instance extracted from the given salt and key.
+     *
+     * <p>Both the salt and input key value may be of arbitrary size, but it is recommended
+     * to have both be at least 16 bytes in size.</p>
+     *
+     * @param salt a non-secret salt value. Should ideally be high entropy and functionally
+     *             "as if random". May not be empty, use {@link #unsaltedExtractedFrom(byte[])}
+     *             if unsalted extraction is desired (though this is not recommended).
+     * @param ikm secret initial Input Keying Material value.
+     * @return a new HDFK instance ready for deriving keys based on the salt and IKM.
+     */
+    public static HKDF extractedFrom(byte[] salt, byte[] ikm) {
+        validateExtractionParams(salt, ikm);
+        /*
+          RFC-5869, Step 2.2, Extract:
+
+          HKDF-Extract(salt, IKM) -> PRK
+
+          Options:
+             Hash     a hash function; HashLen denotes the length of the
+                      hash function output in octets
+
+          Inputs:
+             salt     optional salt value (a non-secret random value);
+                      if not provided, it is set to a string of HashLen zeros.
+             IKM      input keying material
+
+          Output:
+             PRK      a pseudorandom key (of HashLen octets)
+
+          The output PRK is calculated as follows:
+
+          PRK = HMAC-Hash(salt, IKM)
+        */
+        var mac = createKeyedHmacSha256(salt); // Note: HDFK is initially keyed on the salt, _not_ on ikm!
+        mac.update(ikm);
+        return new HKDF(/*PRK = */ mac.doFinal());
+    }
+
+    /**
+     * Creates and returns a new <em>unsalted</em> HKDF instance extracted from the given key.
+     *
+     * <p>Prefer using the salted {@link #extractedFrom(byte[], byte[])} method if possible.</p>
+     *
+     * @param ikm secret initial Input Keying Material value.
+     * @return a new HDFK instance ready for deriving keys based on the IKM and an all-zero salt.
+     */
+    public static HKDF unsaltedExtractedFrom(byte[] ikm) {
+        return extractedFrom(ALL_ZEROS_SALT, ikm);
+    }
+
+    /**
+     * Derives a key with a given number of bytes for a particular context. The returned
+     * key is always deterministic for a given unique context and a HKDF initialized with
+     * a specific salt+IKM pair.
+     *
+     * <p>Thread safety: multiple threads can safely call <code>expand()</code> simultaneously
+     * on the same HKDF object.</p>
+     *
+     * @param wantedBytes Positive number of output bytes. Must be less than or equal to {@link #MAX_OUTPUT_SIZE}
+     * @param context Context for key derivation. Derivation is deterministic for a given context.
+     *                Note: this maps to the "info" field in RFC-5869.
+     * @return A byte buffer of size wantedBytes filled with derived key material
+     */
+    public byte[] expand(int wantedBytes, byte[] context) {
+        Objects.requireNonNull(context);
+        verifyWantedBytesWithinBounds(wantedBytes);
+        return expandImpl(wantedBytes, context);
+    }
+
+    /**
+     * Derives a key with a given number of bytes. The returned key is always deterministic
+     * for a HKDF initialized with a specific salt+IKM pair.
+     *
+     * <p>If more than one key is to be derived, use {@link #expand(int, byte[])}</p>
+     *
+     * <p>Thread safety: multiple threads can safely call <code>expand()</code> simultaneously
+     * on the same HKDF object.</p>
+     *
+     * @param wantedBytes Positive number of output bytes. Must be less than or equal to {@link #MAX_OUTPUT_SIZE}
+     * @return A byte buffer of size wantedBytes filled with derived key material
+     */
+    public byte[] expand(int wantedBytes) {
+        return expand(wantedBytes, EMPTY_BYTES);
+    }
+
+    private void verifyWantedBytesWithinBounds(int wantedBytes) {
+        if (wantedBytes <= 0) {
+            throw new IllegalArgumentException("Requested negative or zero number of HKDF output bytes");
+        }
+        if (wantedBytes > MAX_OUTPUT_SIZE) {
+            throw new IllegalArgumentException("Too many requested HKDF output bytes (max %d, got %d)"
+                                               .formatted(MAX_OUTPUT_SIZE, wantedBytes));
+        }
+    }
+
+    private byte[] expandImpl(int wantedBytes, byte[] context) {
+        /*
+           RFC-5869, Step 2.3, Expand:
+
+           HKDF-Expand(PRK, info, L) -> OKM
+
+           Inputs:
+              PRK      a pseudorandom key of at least HashLen octets
+                       (usually, the output from the extract step)
+              info     optional context and application specific information
+                       (can be a zero-length string)
+              L        length of output keying material in octets
+                       (<= 255*HashLen)
+
+           Output:
+              OKM      output keying material (of L octets)
+
+           The output OKM is calculated as follows:
+
+           N = ceil(L/HashLen)
+           T = T(1) | T(2) | T(3) | ... | T(N)
+           OKM = first L octets of T
+
+           where:
+           T(0) = empty string (zero length)
+           T(1) = HMAC-Hash(PRK, T(0) | info | 0x01)
+           T(2) = HMAC-Hash(PRK, T(1) | info | 0x02)
+           T(3) = HMAC-Hash(PRK, T(2) | info | 0x03)
+           ...
+        */
+        var prkHmac = createKeyedHmacSha256(pseudoRandomKey);
+        int blocks  = (wantedBytes / HASH_LEN) + ((wantedBytes % HASH_LEN) != 0 ? 1 : 0); // N
+        var buffer  = ByteBuffer.allocate(blocks * HASH_LEN); // T
+        byte[] lastBlock = EMPTY_BYTES; // initially T(0)
+        for (int i = 0; i < blocks; ++i) {
+            prkHmac.update(lastBlock);
+            prkHmac.update(context);
+            prkHmac.update((byte)(i + 1)); // Number of blocks shall never exceed 255
+            // HMAC instance can be reused across doFinal() calls; resets back to initially keyed state.
+            lastBlock = prkHmac.doFinal();
+            buffer.put(lastBlock);
+        }
+        buffer.flip();
+        byte[] outputKeyingMaterial = new byte[wantedBytes]; // OKM
+        buffer.get(outputKeyingMaterial);
+        return outputKeyingMaterial;
+    }
+
+}