diff --git a/lib/decoding/osmocom/crypt/auth.h b/lib/decoding/osmocom/crypt/auth.h
new file mode 100644
index 0000000..5c45a5d
--- /dev/null
+++ b/lib/decoding/osmocom/crypt/auth.h
@@ -0,0 +1,111 @@
+#pragma once
+
+/*! \defgroup auth GSM/GPRS/3G Authentication
+ *  @{
+ * \file auth.h */
+
+#include <stdint.h>
+
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/utils.h>
+
+#define OSMO_A5_MAX_KEY_LEN_BYTES (128/8)
+#define OSMO_MILENAGE_IND_BITLEN_MAX 28
+
+/*! Authentication Type (GSM/UMTS) */
+enum osmo_sub_auth_type {
+	OSMO_AUTH_TYPE_NONE	= 0x00,
+	OSMO_AUTH_TYPE_GSM	= 0x01,
+	OSMO_AUTH_TYPE_UMTS	= 0x02,
+};
+
+extern const struct value_string osmo_sub_auth_type_names[];
+/*static inline const char *osmo_sub_auth_type_name(enum osmo_sub_auth_type val)
+{ return get_value_string(osmo_sub_auth_type_names, val); }
+*/
+
+/*! Authentication Algorithm.
+ * See also osmo_auth_alg_name() and osmo_auth_alg_parse(). */
+enum osmo_auth_algo {
+	OSMO_AUTH_ALG_NONE,
+	OSMO_AUTH_ALG_COMP128v1,
+	OSMO_AUTH_ALG_COMP128v2,
+	OSMO_AUTH_ALG_COMP128v3,
+	OSMO_AUTH_ALG_XOR,
+	OSMO_AUTH_ALG_MILENAGE,
+	_OSMO_AUTH_ALG_NUM,
+};
+
+/*! permanent (secret) subscriber auth data */
+struct osmo_sub_auth_data {
+	enum osmo_sub_auth_type type;
+	enum osmo_auth_algo algo;
+	union {
+		struct {
+			uint8_t opc[16]; /*!< operator invariant value */
+			uint8_t k[16];	/*!< secret key of the subscriber */
+			uint8_t amf[2];
+			uint64_t sqn;	/*!< sequence number (in: prev sqn; out: used sqn) */
+			int opc_is_op;	/*!< is the OPC field OPC (0) or OP (1) ? */
+			unsigned int ind_bitlen; /*!< nr of bits not in SEQ, only SQN */
+			unsigned int ind; /*!< which IND slot to use an SQN from */
+			uint64_t sqn_ms; /*!< sqn from AUTS (output value only) */
+		} umts;
+		struct {
+			uint8_t ki[OSMO_A5_MAX_KEY_LEN_BYTES];	/*!< secret key */
+		} gsm;
+	} u;
+};
+
+/* data structure describing a computed auth vector, generated by AuC */
+struct osmo_auth_vector {
+	uint8_t rand[16];	/*!< random challenge */
+	uint8_t autn[16];	/*!< authentication nonce */
+	uint8_t ck[16];		/*!< ciphering key */
+	uint8_t ik[16];		/*!< integrity key */
+	uint8_t res[16];	/*!< authentication result */
+	uint8_t res_len;	/*!< length (in bytes) of res */
+	uint8_t kc[8];		/*!< Kc for GSM encryption (A5) */
+	uint8_t sres[4];	/*!< authentication result for GSM */
+	uint32_t auth_types;	/*!< bitmask of OSMO_AUTH_TYPE_* */
+};
+
+/* An implementation of an authentication algorithm */
+struct osmo_auth_impl {
+	struct llist_head list;
+	enum osmo_auth_algo algo; /*!< algorithm we implement */
+	const char *name;	/*!< name of the implementation */
+	unsigned int priority;	/*!< priority value (resp. othe implementations */
+
+	/*! callback for generate authentication vectors */
+	int (*gen_vec)(struct osmo_auth_vector *vec,
+			struct osmo_sub_auth_data *aud,
+			const uint8_t *_rand);
+
+	/* callback for generationg auth vectors + re-sync */
+	int (*gen_vec_auts)(struct osmo_auth_vector *vec,
+			    struct osmo_sub_auth_data *aud,
+			    const uint8_t *auts, const uint8_t *rand_auts,
+			    const uint8_t *_rand);
+};
+
+int osmo_auth_gen_vec(struct osmo_auth_vector *vec,
+		      struct osmo_sub_auth_data *aud, const uint8_t *_rand);
+
+int osmo_auth_gen_vec_auts(struct osmo_auth_vector *vec,
+			   struct osmo_sub_auth_data *aud,
+			   const uint8_t *auts, const uint8_t *rand_auts,
+			   const uint8_t *_rand);
+
+int osmo_auth_register(struct osmo_auth_impl *impl);
+
+int osmo_auth_load(const char *path);
+
+int osmo_auth_supported(enum osmo_auth_algo algo);
+void osmo_c4(uint8_t *ck, const uint8_t *kc);
+const char *osmo_auth_alg_name(enum osmo_auth_algo alg);
+//enum osmo_auth_algo osmo_auth_alg_parse(const char *name);
+
+void osmo_auth_c3(uint8_t kc[], const uint8_t ck[], const uint8_t ik[]);
+
+/* @} */