diff --git a/src/gsm/kdf/sha1.c b/src/gsm/kdf/sha1.c
new file mode 100644
index 0000000..0d39f77
--- /dev/null
+++ b/src/gsm/kdf/sha1.c
@@ -0,0 +1,162 @@
+/*
+ * SHA1 hash implementation and interface functions
+ * Copyright (c) 2003-2005, Jouni Malinen <j@w1.fi>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Alternatively, this software may be distributed under the terms of BSD
+ * license.
+ *
+ * See README and COPYING for more details.
+ */
+
+
+#include "common.h"
+#include "sha1.h"
+#include "crypto.h"
+
+
+/**
+ * hmac_sha1_vector - HMAC-SHA1 over data vector (RFC 2104)
+ * @key: Key for HMAC operations
+ * @key_len: Length of the key in bytes
+ * @num_elem: Number of elements in the data vector
+ * @addr: Pointers to the data areas
+ * @len: Lengths of the data blocks
+ * @mac: Buffer for the hash (20 bytes)
+ * Returns: 0 on success, -1 on failure
+ */
+int hmac_sha1_vector(const u8 *key, size_t key_len, size_t num_elem,
+		     const u8 *addr[], const size_t *len, u8 *mac)
+{
+	unsigned char k_pad[64]; /* padding - key XORd with ipad/opad */
+	unsigned char tk[20];
+	const u8 *_addr[6];
+	size_t _len[6], i;
+
+	if (num_elem > 5) {
+		/*
+		 * Fixed limit on the number of fragments to avoid having to
+		 * allocate memory (which could fail).
+		 */
+		return -1;
+	}
+
+        /* if key is longer than 64 bytes reset it to key = SHA1(key) */
+        if (key_len > 64) {
+		if (sha1_vector(1, &key, &key_len, tk))
+			return -1;
+		key = tk;
+		key_len = 20;
+        }
+
+	/* the HMAC_SHA1 transform looks like:
+	 *
+	 * SHA1(K XOR opad, SHA1(K XOR ipad, text))
+	 *
+	 * where K is an n byte key
+	 * ipad is the byte 0x36 repeated 64 times
+	 * opad is the byte 0x5c repeated 64 times
+	 * and text is the data being protected */
+
+	/* start out by storing key in ipad */
+	os_memset(k_pad, 0, sizeof(k_pad));
+	os_memcpy(k_pad, key, key_len);
+	/* XOR key with ipad values */
+	for (i = 0; i < 64; i++)
+		k_pad[i] ^= 0x36;
+
+	/* perform inner SHA1 */
+	_addr[0] = k_pad;
+	_len[0] = 64;
+	for (i = 0; i < num_elem; i++) {
+		_addr[i + 1] = addr[i];
+		_len[i + 1] = len[i];
+	}
+	if (sha1_vector(1 + num_elem, _addr, _len, mac))
+		return -1;
+
+	os_memset(k_pad, 0, sizeof(k_pad));
+	os_memcpy(k_pad, key, key_len);
+	/* XOR key with opad values */
+	for (i = 0; i < 64; i++)
+		k_pad[i] ^= 0x5c;
+
+	/* perform outer SHA1 */
+	_addr[0] = k_pad;
+	_len[0] = 64;
+	_addr[1] = mac;
+	_len[1] = SHA1_MAC_LEN;
+	return sha1_vector(2, _addr, _len, mac);
+}
+
+
+/**
+ * hmac_sha1 - HMAC-SHA1 over data buffer (RFC 2104)
+ * @key: Key for HMAC operations
+ * @key_len: Length of the key in bytes
+ * @data: Pointers to the data area
+ * @data_len: Length of the data area
+ * @mac: Buffer for the hash (20 bytes)
+ * Returns: 0 on success, -1 of failure
+ */
+int hmac_sha1(const u8 *key, size_t key_len, const u8 *data, size_t data_len,
+	       u8 *mac)
+{
+	return hmac_sha1_vector(key, key_len, 1, &data, &data_len, mac);
+}
+
+
+/**
+ * sha1_prf - SHA1-based Pseudo-Random Function (PRF) (IEEE 802.11i, 8.5.1.1)
+ * @key: Key for PRF
+ * @key_len: Length of the key in bytes
+ * @label: A unique label for each purpose of the PRF
+ * @data: Extra data to bind into the key
+ * @data_len: Length of the data
+ * @buf: Buffer for the generated pseudo-random key
+ * @buf_len: Number of bytes of key to generate
+ * Returns: 0 on success, -1 of failure
+ *
+ * This function is used to derive new, cryptographically separate keys from a
+ * given key (e.g., PMK in IEEE 802.11i).
+ */
+int sha1_prf(const u8 *key, size_t key_len, const char *label,
+	     const u8 *data, size_t data_len, u8 *buf, size_t buf_len)
+{
+	u8 counter = 0;
+	size_t pos, plen;
+	u8 hash[SHA1_MAC_LEN];
+	size_t label_len = os_strlen(label) + 1;
+	const unsigned char *addr[3];
+	size_t len[3];
+
+	addr[0] = (u8 *) label;
+	len[0] = label_len;
+	addr[1] = data;
+	len[1] = data_len;
+	addr[2] = &counter;
+	len[2] = 1;
+
+	pos = 0;
+	while (pos < buf_len) {
+		plen = buf_len - pos;
+		if (plen >= SHA1_MAC_LEN) {
+			if (hmac_sha1_vector(key, key_len, 3, addr, len,
+					     &buf[pos]))
+				return -1;
+			pos += SHA1_MAC_LEN;
+		} else {
+			if (hmac_sha1_vector(key, key_len, 3, addr, len,
+					     hash))
+				return -1;
+			os_memcpy(&buf[pos], hash, plen);
+			break;
+		}
+		counter++;
+	}
+
+	return 0;
+}