An example of how to use ML-KEM.

pq/ml_kem/README.md

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+# Description
+
+Simple example of wolfCrypt ML-KEM keygen, encapsulation, and decapsulation.
+
+Requires wolfSSL is built with:
+
+```sh
+$ ./autogen.sh
+$ ./configure --enable-mlkem
+$ make
+$ sudo make install
+$ sudo ldconfig
+```
+
+Build the ML-KEM example:
+
+```sh
+$ gcc -o ml_kem ml_kem.c -I/usr/local/include -L/usr/local/lib -lwolfssl
+```
+
+# Usage
+
+```
+./ml_kem
+```
+
+Alice will generate a public key and private key pair. The operation is known as
+key generation.
+
+Bob will use only Alice's public key to generate a shared secret and an
+ecapsulated instance of the shared secret; this is known as the ciphertext. The
+operation is known as encapsulation.
+
+Alice will use Bob's ciphertext and her private key to obtain the same shared
+secret. The operation is known as decapsulation.
+
+# Credit
+
+The wolfSSL Team would like to thank Professor Bill Buchanan of Edinburgh Napier
+University for initially creating this example.

pq/ml_kem/ml_kem.c

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+/* ml_kem.c
+ *
+ * Copyright (C) 2025 wolfSSL Inc.
+ *
+ * This file is part of wolfSSL. (formerly known as CyaSSL)
+ *
+ * wolfSSL is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * wolfSSL is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
+ */
+
+/* Credit goes to Professor Bill Buchanan of Edinburgh Napier University for
+ * creating this example and contributing it back to wolfSSL. */
+
+#ifndef WOLFSSL_USER_SETTINGS
+    #include <wolfssl/options.h>
+#endif
+#include <wolfssl/wolfcrypt/settings.h>
+#include <wolfssl/wolfcrypt/mlkem.h>
+#include <wolfssl/wolfcrypt/wc_mlkem.h>
+#include <wolfssl/wolfcrypt/random.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+
+char* to_hex_string(const unsigned char* array, size_t length)
+{
+    char* outstr = malloc(2 * length + 1);
+    if (!outstr) return outstr;
+
+    char* p = outstr;
+    for (size_t i = 0; i < length; ++i) {
+        p += sprintf(p, "%02hhx", array[i]);
+    }
+
+    return outstr;
+}
+
+
+int main(int argc, char** argv)
+{
+    MlKemKey AliceKey;
+    MlKemKey BobKey;
+    int ret = 0;
+    WC_RNG rng;
+    byte alice_pub[WC_ML_KEM_512_PUBLIC_KEY_SIZE];
+    byte bob_ct[WC_ML_KEM_512_CIPHER_TEXT_SIZE];
+    byte alice_ss[WC_ML_KEM_SS_SZ];
+    byte bob_ss[WC_ML_KEM_SS_SZ];
+
+    printf("Alice creates an ML-KEM-512 key pair\n\n");
+
+    ret = wc_InitRng(&rng);
+
+    if (ret == 0)
+        ret = wc_MlKemKey_Init(&AliceKey, WC_ML_KEM_512, 0, INVALID_DEVID);
+
+    if (ret == 0)
+        ret = wc_MlKemKey_Init(&BobKey, WC_ML_KEM_512, 0, INVALID_DEVID);
+
+    if (ret == 0)
+        ret = wc_MlKemKey_MakeKey(&AliceKey, &rng);
+
+    if (ret == 0)
+        ret = wc_MlKemKey_EncodePublicKey(&AliceKey, alice_pub, WC_ML_KEM_512_PUBLIC_KEY_SIZE);
+
+    if (ret == 0)
+        printf("Bob receives public key (size=%d): %s\n\n", WC_ML_KEM_512_PUBLIC_KEY_SIZE, to_hex_string(alice_pub, WC_ML_KEM_512_PUBLIC_KEY_SIZE));
+
+    if (ret == 0)
+        ret = wc_MlKemKey_DecodePublicKey(&BobKey, alice_pub, WC_ML_KEM_512_PUBLIC_KEY_SIZE);
+
+    if (ret == 0)
+        ret = wc_MlKemKey_Encapsulate(&BobKey, bob_ct, bob_ss, &rng);
+
+    if (ret == 0)
+        printf("Bob Encapsulates secret (Size=%d): %s\n\n", WC_ML_KEM_512_CIPHER_TEXT_SIZE, to_hex_string(bob_ct, WC_ML_KEM_512_CIPHER_TEXT_SIZE));
+
+    if (ret == 0)
+        printf("Alice receives the ciphertext\n");
+
+    if (ret == 0)
+        ret = wc_MlKemKey_Decapsulate(&AliceKey, alice_ss, bob_ct, WC_ML_KEM_512_CIPHER_TEXT_SIZE);
+
+    if (ret == 0) {
+        printf("Alice's Shared Secret: %s\n\n", to_hex_string(alice_ss, WC_ML_KEM_SS_SZ));
+        printf("  Bob's Shared Secret: %s\n\n", to_hex_string(bob_ss, WC_ML_KEM_SS_SZ));
+    } else {
+        printf("An error occurred\n");
+    }
+
+    wc_MlKemKey_Free(&AliceKey);
+    wc_MlKemKey_Free(&BobKey);
+    wc_FreeRng(&rng);
+    return ret;
+}
+