diff --git a/utils/osmo-aka-verify.c b/utils/osmo-aka-verify.c
new file mode 100644
index 0000000..5134d79
--- /dev/null
+++ b/utils/osmo-aka-verify.c
@@ -0,0 +1,243 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <getopt.h>
+
+#include <osmocom/core/utils.h>
+#include <osmocom/core/bit64gen.h>
+
+/* Utility program for implementing the SIM-side procedures of 3GPP Authentication and Key Agreement
+ * as specified by 3GPP TS 33.102 Section 6.3.3
+ *
+ * (C) 2021 by Harald Welte <laforge@gnumonks.org>
+ * Milenage library code used from libosmocore, which inherited it from wpa_supplicant
+ */
+
+/* FIXME: libosmogsm implements those, but doesn't declare them */
+int milenage_f1(const uint8_t *opc, const uint8_t *k, const uint8_t *_rand,
+		const uint8_t *sqn, const uint8_t *amf, uint8_t *mac_a, uint8_t *mac_s);
+int milenage_f2345(const uint8_t *opc, const uint8_t *k, const uint8_t *_rand,
+		   uint8_t *res, uint8_t *ck, uint8_t *ik, uint8_t *ak, uint8_t *akstar);
+
+static int milenage_check(const uint8_t *opc, const uint8_t *k, const uint8_t *sqn, const uint8_t *_rand,
+			  const uint8_t *autn, uint8_t *ik, uint8_t *ck, uint8_t *res, size_t *res_len,
+			  uint8_t *auts)
+{
+	int i;
+	uint8_t xmac[8], ak[6], rx_sqn_bin[6];
+	unsigned long long rx_sqn;
+	const uint8_t *amf;
+
+	printf("=== Static SIM parameters:\n");
+	printf("Milenage SIM K: %s\n", osmo_hexdump_nospc(k, 16));
+	printf("Milenage SIM OPc: %s\n", osmo_hexdump_nospc(opc, 16));
+	printf("Milenage SIM SQN: %s\n", osmo_hexdump_nospc(sqn, 6));
+	printf("\n");
+
+	printf("=== Authentication Tuple as received from Network:\n");
+	printf("Milenage Input RAND: %s\n", osmo_hexdump_nospc(_rand, 16));
+	printf("Milenage Input AUTN: %s\n", osmo_hexdump_nospc(autn, 16));
+	printf("\tAUTN(+)AK: %s\n", osmo_hexdump_nospc(autn, 6));
+	printf("\tAMF: %s\n", osmo_hexdump_nospc(autn+6, 2));
+	printf("\tMAC: %s\n", osmo_hexdump_nospc(autn+8, 8));
+	printf("\n");
+
+	if (milenage_f2345(opc, k, _rand, res, ck, ik, ak, NULL))
+		return -1;
+
+	*res_len = 8;
+	printf("Milenage f2-Computed RES: %s\n", osmo_hexdump_nospc(res, *res_len));
+	printf("Milenage f3-Computed CK: %s\n", osmo_hexdump_nospc(ck, 16));
+	printf("Milenage f4-Computed IK: %s\n", osmo_hexdump_nospc(ik, 16));
+	printf("Milenage f5-Computed AK: %s\n", osmo_hexdump_nospc(ak, 6));
+
+	/* AUTN = (SQN ^ AK) || AMF || MAC */
+	for (i = 0; i < 6; i++)
+		rx_sqn_bin[i] = autn[i] ^ ak[i];
+	rx_sqn = osmo_load64be_ext(rx_sqn_bin, 6);
+	printf("Milenage Computed SQN: %s (%llu)\n", osmo_hexdump_nospc(rx_sqn_bin, 6), rx_sqn);
+
+	if (memcmp(rx_sqn_bin, sqn, 6) <= 0) {
+		printf("Milenage: RX-SQN differs from SIM SQN: Re-Sync!\n");
+		uint8_t auts_amf[2] = { 0x00, 0x00 }; /* TS 33.102 v7.0.0, 6.3.3 */
+		if (milenage_f2345(opc, k, _rand, NULL, NULL, NULL, NULL, ak))
+			return -1;
+		printf("Milenage Computed AK*: %s", osmo_hexdump_nospc(ak, 6));
+		for (i = 0; i < 6; i++)
+			auts[i] = sqn[i] ^ ak[i];
+		if (milenage_f1(opc, k, _rand, sqn, auts_amf, NULL, auts + 6))
+			return -1;
+		printf("Milenage AUTS: %s\n", osmo_hexdump_nospc(auts, 14));
+		return -2;
+	}
+
+	amf = autn + 6;
+	if (milenage_f1(opc, k, _rand, rx_sqn_bin, amf, xmac, NULL))
+		return -1;
+
+	printf("Milenage f1-Computed XMAC: %s\n", osmo_hexdump_nospc(xmac, 8));
+
+	if (memcmp(xmac, autn + 8, 8) != 0) {
+		fprintf(stderr, "Milenage: MAC mismatch!\n");
+		return -1;
+	}
+
+	return 0;
+}
+
+
+static void help()
+{
+	printf( "Static SIM card parameters:\n"
+		"-k  --key\tSpecify Ki / K\n"
+		"-o  --opc\tSpecify OPC\n"
+		"-O  --op\tSpecify OP\n"
+		"-f  --amf\tSpecify AMF\n"
+		"-s  --sqn\tSpecify SQN\n"
+	        "\n"
+	        "Authentication Tuple by network:\n"
+		//"-i  --ind\tSpecify IND slot for new SQN after AUTS\n"
+		//"-l  --ind-len\tSpecify IND bit length (default=5)\n"
+		"-r  --rand\tSpecify RAND random value\n"
+		"-A  --autn\tSpecify AUTN authentication nonce\n"
+	      );
+}
+
+static uint8_t g_k[16];
+static uint8_t g_opc[16];
+static uint8_t g_rand[16];
+static uint8_t g_autn[16];
+static uint8_t g_amf[16];
+static unsigned long long g_sqn;
+
+
+static int handle_options(int argc, char **argv)
+{
+	int rc, option_index;
+	bool rand_is_set = false;
+	bool autn_is_set = false;
+	bool sqn_is_set = false;
+	bool k_is_set = false;
+	bool opc_is_set = false;
+	bool amf_is_set = false;
+	bool opc_is_op = false;
+
+	while (1) {
+		int c;
+		static struct option long_options[] = {
+			{ "key", 1, 0, 'k' },
+			{ "opc", 1, 0, 'o' },
+			{ "op", 1, 0, 'O' },
+			{ "amf", 1, 0, 'f' },
+			{ "sqn", 1, 0, 's' },
+			{ "rand", 1, 0, 'r' },
+			{ "autn", 1, 0, 'A' },
+			{ "help", 0, 0, 'h' },
+			{ 0, 0, 0, 0 }
+		};
+
+		rc = 0;
+
+		c = getopt_long(argc, argv, "k:o:O:f:s:r:A:h", long_options, &option_index);
+
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 'k':
+			rc = osmo_hexparse(optarg, g_k, sizeof(g_k));
+			k_is_set = true;
+			break;
+		case 'o':
+			rc = osmo_hexparse(optarg, g_opc, sizeof(g_opc));
+			opc_is_op = false;
+			opc_is_set = true;
+			break;
+		case 'O':
+			rc = osmo_hexparse(optarg, g_opc, sizeof(g_opc));
+			opc_is_op = true;
+			opc_is_set = true;
+			break;
+		case 'A':
+			rc = osmo_hexparse(optarg, g_autn, sizeof(g_autn));
+			autn_is_set = true;
+			break;
+		case 'f':
+			rc = osmo_hexparse(optarg, g_amf, sizeof(g_amf));
+			amf_is_set = true;
+			break;
+		case 's':
+			g_sqn = strtoull(optarg, 0, 10);
+			sqn_is_set = true;
+			break;
+		case 'r':
+			rc = osmo_hexparse(optarg, g_rand, sizeof(g_rand));
+			rand_is_set = true;
+			break;
+		case 'h':
+			help();
+			exit(0);
+		default:
+			help();
+			exit(1);
+		}
+
+		if (rc < 0) {
+			help();
+			fprintf(stderr, "\nError parsing argument of option `%c'\n", c);
+			exit(2);
+		}
+	}
+
+	if (!k_is_set || !opc_is_set || !autn_is_set || !rand_is_set) {
+		fprintf(stderr, "Error: K, OP[c], AUTN and RAND are mandatory arguments\n");
+		fprintf(stderr, "\n");
+		help();
+		exit(2);
+	}
+
+	if (!sqn_is_set)
+		printf("Warning: You may want to specify SQN\n");
+
+	if (!amf_is_set)
+		printf("Warning: You may want to specify AMF\n");
+
+	if (opc_is_op) {
+		/* FIXME */
+	}
+
+	return 0;
+}
+
+
+
+int main(int argc, char **argv)
+{
+	printf("osmo-aka-check (C) 2021 by Harald Welte\n");
+	printf("This is FREE SOFTWARE with ABSOLUTELY NO WARRANTY\n\n");
+
+	handle_options(argc, argv);
+
+	printf("\n");
+
+	uint8_t ck[16];
+	uint8_t ik[16];
+	uint8_t res[16];
+	size_t res_len;
+	uint8_t auts[14];
+	uint8_t sqn_bin[6];
+	int rc;
+
+	osmo_store64be_ext(g_sqn, sqn_bin, 6);
+
+	rc = milenage_check(g_opc, g_k, sqn_bin, g_rand, g_autn, ck, ik, res, &res_len, auts);
+
+	if (rc < 0) {
+		fprintf(stderr, "Authentication FAILED!\n");
+		exit(1);
+	} else {
+		printf("Authentication SUCCEEDED\n");
+		exit(0);
+	}
+}