diff --git a/configure.ac b/configure.ac

index 9f8b31b..38781da 100755

--- a/configure.ac

+++ b/configure.ac

@@ -529,6 +529,20 @@ AC_ARG_ENABLE([thread-sanitizer],

   AS_HELP_STRING([--enable-thread-sanitizer], [enable ThreadSanitizer support for detecting data races]))

 AC_ARG_ENABLE([memory-sanitizer],

   AS_HELP_STRING([--enable-memory-sanitizer], [enable MemorySanitizer support for detecting uninitialized memory reads]))

+AC_ARG_WITH([crypto],

+  AS_HELP_STRING([--with-crypto=<internal|openssl>], [choose between different implementations of cryptographic functions(default value is --with-crypto=internal)]))

+

+#if openssl, else use internal as default

+AS_IF([test x"${with_crypto}" = x"openssl"], [

+  AC_CHECK_LIB([crypto], [EVP_DigestInit], [LIBS="$LIBS -lcrypto"], [], [])

+  if test "$ac_cv_lib_crypto_EVP_DigestInit" = no; then

+    AC_MSG_ERROR([build with openssl has been specified but openssl library was not found on your system])

+  else

+    AC_DEFINE([CRYPTO_OPENSSL], [1], [Compile with openssl support])

+  fi

+], [test x"${with_crypto}" = x"internal" || test x"${with_crypto}" = x"" ], [AC_DEFINE([CRYPTO_INTERNAL], [1], [Compile with internal cryptographic implementation])

+], [AC_MSG_ERROR([Unknown value for --with-crypto])]

+)

 AS_IF([test "${enable_clippy_only}" != "yes"], [

 AC_CHECK_HEADERS([json-c/json.h])

diff --git a/lib/subdir.am b/lib/subdir.am

index 0b7af18..0533e24 100644

--- a/lib/subdir.am

+++ b/lib/subdir.am

@@ -41,7 +41,6 @@ lib_libfrr_la_SOURCES = \

 	lib/libfrr.c \

 	lib/linklist.c \

 	lib/log.c \

-	lib/md5.c \

 	lib/memory.c \

 	lib/memory_vty.c \

 	lib/module.c \

diff --git a/lib/subdir.am b/lib/subdir.am

index 0533e24..b3d3700 100644

--- a/lib/subdir.am

+++ b/lib/subdir.am

@@ -170,7 +170,6 @@ pkginclude_HEADERS += \

 	lib/libospf.h \

 	lib/linklist.h \

 	lib/log.h \

-	lib/md5.h \

 	lib/memory.h \

 	lib/memory_vty.h \

 	lib/module.h \

diff --git a/lib/subdir.am b/lib/subdir.am

index 53f7115..cea866f 100644

--- a/lib/subdir.am

+++ b/lib/subdir.am

@@ -64,7 +64,6 @@ lib_libfrr_la_SOURCES = \

 	lib/ringbuf.c \

 	lib/routemap.c \

 	lib/sbuf.c \

-	lib/sha256.c \

 	lib/sigevent.c \

 	lib/skiplist.c \

 	lib/sockopt.c \

@@ -191,7 +190,6 @@ pkginclude_HEADERS += \

 	lib/ringbuf.h \

 	lib/routemap.h \

 	lib/sbuf.h \

-	lib/sha256.h \

 	lib/sigevent.h \

 	lib/skiplist.h \

 	lib/smux.h \

diff --git a/lib/zebra.h b/lib/zebra.h

index 22239f8e60..a308d46cc9 100644

--- a/lib/zebra.h

+++ b/lib/zebra.h

@@ -134,6 +134,11 @@ typedef unsigned char uint8_t;

 #endif

 #endif

+#ifdef CRYPTO_OPENSSL

+#include <openssl/evp.h>

+#include <openssl/hmac.h>

+#endif

+

 #include "openbsd-tree.h"

 #include <netinet/in.h>

diff --git a/ospfd/ospf_packet.c b/ospfd/ospf_packet.c

index 6bc8c25153..b951e94ae6 100644

--- a/ospfd/ospf_packet.c

+++ b/ospfd/ospf_packet.c

@@ -33,7 +33,9 @@

 #include "log.h"

 #include "sockopt.h"

 #include "checksum.h"

+#if  !defined(CRYPTO_OPENSSL) && !defined(HAVE_NETTLE)

 #include "md5.h"

+#endif

 #include "vrf.h"

 #include "lib_errors.h"

@@ -332,7 +334,11 @@ static unsigned int ospf_packet_max(struct ospf_interface *oi)

 static int ospf_check_md5_digest(struct ospf_interface *oi,

 				 struct ospf_header *ospfh)

 {

+#ifdef CRYPTO_OPENSSL

+	EVP_MD_CTX *ctx;

+#else

 	MD5_CTX ctx;

+#endif

 	unsigned char digest[OSPF_AUTH_MD5_SIZE];

 	struct crypt_key *ck;

 	struct ospf_neighbor *nbr;

@@ -361,11 +367,21 @@ static int ospf_check_md5_digest(struct ospf_interface *oi,

 	}

 	/* Generate a digest for the ospf packet - their digest + our digest. */

+#ifdef CRYPTO_OPENSSL

+	unsigned int md5_size = OSPF_AUTH_MD5_SIZE;

+	ctx = EVP_MD_CTX_new();

+	EVP_DigestInit(ctx, EVP_md5());

+	EVP_DigestUpdate(ctx, ospfh, length);

+	EVP_DigestUpdate(ctx, ck->auth_key, OSPF_AUTH_MD5_SIZE);

+	EVP_DigestFinal(ctx, digest, &md5_size);

+	EVP_MD_CTX_free(ctx);

+#elif CRYPTO_INTERNAL

 	memset(&ctx, 0, sizeof(ctx));

 	MD5Init(&ctx;;

 	MD5Update(&ctx, ospfh, length);

 	MD5Update(&ctx, ck->auth_key, OSPF_AUTH_MD5_SIZE);

 	MD5Final(digest, &ctx;;

+#endif

 	/* compare the two */

 	if (memcmp((caddr_t)ospfh + length, digest, OSPF_AUTH_MD5_SIZE)) {

@@ -389,7 +404,11 @@ static int ospf_make_md5_digest(struct ospf_interface *oi,

 {

 	struct ospf_header *ospfh;

 	unsigned char digest[OSPF_AUTH_MD5_SIZE] = {0};

+#ifdef CRYPTO_OPENSSL

+	EVP_MD_CTX *ctx;

+#else

 	MD5_CTX ctx;

+#endif

 	void *ibuf;

 	uint32_t t;

 	struct crypt_key *ck;

@@ -422,11 +441,21 @@ static int ospf_make_md5_digest(struct ospf_interface *oi,

 	}

 	/* Generate a digest for the entire packet + our secret key. */

+#ifdef CRYPTO_OPENSSL

+	unsigned int md5_size = OSPF_AUTH_MD5_SIZE;

+	ctx = EVP_MD_CTX_new();

+	EVP_DigestInit(ctx, EVP_md5());

+	EVP_DigestUpdate(ctx, ibuf, ntohs(ospfh->length));

+	EVP_DigestUpdate(ctx, auth_key, OSPF_AUTH_MD5_SIZE);

+	EVP_DigestFinal(ctx, digest, &md5_size);

+	EVP_MD_CTX_free(ctx);

+#elif CRYPTO_INTERNAL

 	memset(&ctx, 0, sizeof(ctx));

 	MD5Init(&ctx;;

 	MD5Update(&ctx, ibuf, ntohs(ospfh->length));

 	MD5Update(&ctx, auth_key, OSPF_AUTH_MD5_SIZE);

 	MD5Final(digest, &ctx;;

+#endif

 	/* Append md5 digest to the end of the stream. */

 	stream_put(op->s, digest, OSPF_AUTH_MD5_SIZE);

diff --git a/ripd/ripd.c b/ripd/ripd.c

index e0ff0430f8..b311ac5717 100644

--- a/ripd/ripd.c

+++ b/ripd/ripd.c

@@ -37,7 +37,9 @@

 #include "if_rmap.h"

 #include "plist.h"

 #include "distribute.h"

+#if !defined(CRYPTO_OPENSSL) && !defined(HAVE_NETTLE)

 #include "md5.h"

+#endif

 #include "keychain.h"

 #include "privs.h"

 #include "lib_errors.h"

@@ -870,7 +872,11 @@ static int rip_auth_md5(struct rip_packet *packet, struct sockaddr_in *from,

 	struct rip_md5_data *md5data;

 	struct keychain *keychain;

 	struct key *key;

+#ifdef CRYPTO_OPENSSL

+	EVP_MD_CTX *ctx;

+#else

 	MD5_CTX ctx;

+#endif

 	uint8_t digest[RIP_AUTH_MD5_SIZE];

 	uint16_t packet_len;

 	char auth_str[RIP_AUTH_MD5_SIZE];

@@ -934,11 +940,21 @@ static int rip_auth_md5(struct rip_packet *packet, struct sockaddr_in *from,

 		return 0;

 	/* MD5 digest authentication. */

+#ifdef CRYPTO_OPENSSL

+	unsigned int md5_size = RIP_AUTH_MD5_SIZE;

+	ctx = EVP_MD_CTX_new();

+	EVP_DigestInit(ctx, EVP_md5());

+	EVP_DigestUpdate(ctx, packet, packet_len + RIP_HEADER_SIZE);

+	EVP_DigestUpdate(ctx, auth_str, RIP_AUTH_MD5_SIZE);

+	EVP_DigestFinal(ctx, digest, &md5_size);

+	EVP_MD_CTX_free(ctx);

+#elif CRYPTO_INTERNAL

 	memset(&ctx, 0, sizeof(ctx));

 	MD5Init(&ctx;;

 	MD5Update(&ctx, packet, packet_len + RIP_HEADER_SIZE);

 	MD5Update(&ctx, auth_str, RIP_AUTH_MD5_SIZE);

 	MD5Final(digest, &ctx;;

+#endif

 	if (memcmp(md5data->digest, digest, RIP_AUTH_MD5_SIZE) == 0)

 		return packet_len;

@@ -1063,7 +1078,11 @@ static void rip_auth_md5_set(struct stream *s, struct rip_interface *ri,

 			     size_t doff, char *auth_str, int authlen)

 {

 	unsigned long len;

+#ifdef CRYPTO_OPENSSL

+	EVP_MD_CTX *ctx;

+#else

 	MD5_CTX ctx;

+#endif

 	unsigned char digest[RIP_AUTH_MD5_SIZE];

 	/* Make it sure this interface is configured as MD5

@@ -1092,11 +1111,21 @@ static void rip_auth_md5_set(struct stream *s, struct rip_interface *ri,

 	stream_putw(s, RIP_AUTH_DATA);

 	/* Generate a digest for the RIP packet. */

+#ifdef CRYPTO_OPENSSL

+	unsigned int md5_size = RIP_AUTH_MD5_SIZE;

+	ctx = EVP_MD_CTX_new();

+	EVP_DigestInit(ctx, EVP_md5());

+	EVP_DigestUpdate(ctx, STREAM_DATA(s), stream_get_endp(s));

+	EVP_DigestUpdate(ctx, auth_str, RIP_AUTH_MD5_SIZE);

+	EVP_DigestFinal(ctx, digest, &md5_size);

+	EVP_MD_CTX_free(ctx);

+#elif CRYPTO_INTERNAL

 	memset(&ctx, 0, sizeof(ctx));

 	MD5Init(&ctx;;

 	MD5Update(&ctx, STREAM_DATA(s), stream_get_endp(s));

 	MD5Update(&ctx, auth_str, RIP_AUTH_MD5_SIZE);

 	MD5Final(digest, &ctx;;

+#endif

 	/* Copy the digest to the packet. */

 	stream_write(s, digest, RIP_AUTH_MD5_SIZE);

diff --git a/isisd/isis_tlvs.c b/isisd/isis_tlvs.c

index 488dfedae4..862d675e84 100644

--- a/isisd/isis_tlvs.c

+++ b/isisd/isis_tlvs.c

@@ -22,7 +22,9 @@

  */

 #include <zebra.h>

+#ifdef CRYPTO_INTERNAL

 #include "md5.h"

+#endif

 #include "memory.h"

 #include "stream.h"

 #include "sbuf.h"

@@ -2770,8 +2772,13 @@ static void update_auth_hmac_md5(struct isis_auth *auth, struct stream *s,

 		safe_auth_md5(s, &checksum, &rem_lifetime);

 	memset(STREAM_DATA(s) + auth->offset, 0, 16);

+#ifdef CRYPTO_OPENSSL

+	uint8_t* result = (uint8_t*)HMAC(EVP_md5(), auth->passwd, auth->plength, STREAM_DATA(s), stream_get_endp(s), NULL, NULL);

+	memcpy(digest, result, 16);

+#elif  CRYPTO_INTERNAL

 	hmac_md5(STREAM_DATA(s), stream_get_endp(s), auth->passwd,

 		 auth->plength, digest);

+#endif

 	memcpy(auth->value, digest, 16);

 	memcpy(STREAM_DATA(s) + auth->offset, digest, 16);

@@ -3310,8 +3317,13 @@ static bool auth_validator_hmac_md5(struct isis_passwd *passwd,

 		safe_auth_md5(stream, &checksum, &rem_lifetime);

 	memset(STREAM_DATA(stream) + auth->offset, 0, 16);

+#ifdef CRYPTO_OPENSSL

+	uint8_t* result = (uint8_t*)HMAC(EVP_md5(), passwd->passwd, passwd->len, STREAM_DATA(stream), stream_get_endp(stream), NULL, NULL);

+	memcpy(digest, result, 16);

+#elif  CRYPTO_INTERNAL

 	hmac_md5(STREAM_DATA(stream), stream_get_endp(stream), passwd->passwd,

 		 passwd->len, digest);

+#endif

 	memcpy(STREAM_DATA(stream) + auth->offset, auth->value, 16);

 	bool rv = !memcmp(digest, auth->value, 16);

diff --git a/isisd/isis_lsp.c b/isisd/isis_lsp.c

index 1991666..2e4fe55 100644

--- a/isisd/isis_lsp.c

+++ b/isisd/isis_lsp.c

@@ -35,7 +35,9 @@

 #include "hash.h"

 #include "if.h"

 #include "checksum.h"

+#ifdef CRYPTO_INTERNAL

 #include "md5.h"

+#endif

 #include "table.h"

 #include "srcdest_table.h"

 #include "lib_errors.h"

diff --git a/isisd/isis_pdu.c b/isisd/isis_pdu.c

index 9c63311..7cf594c 100644

--- a/isisd/isis_pdu.c

+++ b/isisd/isis_pdu.c

@@ -33,7 +33,9 @@

 #include "prefix.h"

 #include "if.h"

 #include "checksum.h"

+#ifdef CRYPTO_INTERNAL

 #include "md5.h"

+#endif

 #include "lib_errors.h"

 #include "isisd/dict.h"

diff --git a/isisd/isis_te.c b/isisd/isis_te.c

index 4ea6c2c..72ff0d2 100644

--- a/isisd/isis_te.c

+++ b/isisd/isis_te.c

@@ -38,7 +38,9 @@

 #include "if.h"

 #include "vrf.h"

 #include "checksum.h"

+#ifdef CRYPTO_INTERNAL

 #include "md5.h"

+#endif

 #include "sockunion.h"

 #include "network.h"

 #include "sbuf.h"