diff --git a/src/crypto.h b/src/crypto.h
index 97b640e..ad3afa5 100644
--- a/src/crypto.h
+++ b/src/crypto.h
@@ -30,8 +30,8 @@ struct fastd_cipher {
 	/**< Checks if the algorithm is available on the platform used. If NULL, the algorithm is always available. */
 	bool (*available)(void);
 
-	/** Initializes a cipher context with the given key */
-	fastd_cipher_state_t *(*init)(const uint8_t *key);
+	/** Initializes a cipher context with the given key and cipher-specific flags */
+	fastd_cipher_state_t *(*init)(const uint8_t *key, int flags);
 	/** Encrypts or decrypts data */
 	bool (*crypt)(
 		const fastd_cipher_state_t *state, fastd_block128_t *out, const fastd_block128_t *in, size_t len,
@@ -51,8 +51,8 @@ struct fastd_mac {
 	/**< Checks if the algorithm is available on the platform used. If NULL, the algorithm is always available. */
 	bool (*available)(void);
 
-	/** Initializes a MAC context with the given key */
-	fastd_mac_state_t *(*init)(const uint8_t *key);
+	/** Initializes a MAC context with the given key and mac-specific flags */
+	fastd_mac_state_t *(*init)(const uint8_t *key, int flags);
 	/** Computes the MAC of data blocks */
 	bool (*digest)(
 		const fastd_mac_state_t *state, fastd_block128_t *out, const fastd_block128_t *in, size_t length);
diff --git a/src/crypto/cipher/aes128_ctr/openssl/aes128_ctr_openssl.c b/src/crypto/cipher/aes128_ctr/openssl/aes128_ctr_openssl.c
index 5818b33..34ba61d 100644
--- a/src/crypto/cipher/aes128_ctr/openssl/aes128_ctr_openssl.c
+++ b/src/crypto/cipher/aes128_ctr/openssl/aes128_ctr_openssl.c
@@ -14,6 +14,8 @@
 #include "../../../../alloc.h"
 #include "../../../../crypto.h"
 
+#include <assert.h>
+
 #include <openssl/evp.h>
 
 
@@ -24,7 +26,9 @@ struct fastd_cipher_state {
 
 
 /** Initializes the cipher state */
-static fastd_cipher_state_t *aes128_ctr_init(const uint8_t *key) {
+static fastd_cipher_state_t *aes128_ctr_init(const uint8_t *key, UNUSED int flags) {
+	assert(flags == 0);
+
 	fastd_cipher_state_t *state = fastd_new(fastd_cipher_state_t);
 
 	state->aes = EVP_CIPHER_CTX_new();
diff --git a/src/crypto/cipher/null/memcpy/null_memcpy.c b/src/crypto/cipher/null/memcpy/null_memcpy.c
index 6f904f4..e24f434 100644
--- a/src/crypto/cipher/null/memcpy/null_memcpy.c
+++ b/src/crypto/cipher/null/memcpy/null_memcpy.c
@@ -13,9 +13,13 @@
 
 #include "../../../../crypto.h"
 
+#include <assert.h>
+
 
 /** Doesn't do anything as the null cipher doesn't use any state */
-static fastd_cipher_state_t *null_init(UNUSED const uint8_t *key) {
+static fastd_cipher_state_t *null_init(UNUSED const uint8_t *key, UNUSED int flags) {
+	assert(flags == 0);
+
 	return NULL;
 }
 
diff --git a/src/crypto/cipher/salsa20/nacl/salsa20_nacl.c b/src/crypto/cipher/salsa20/nacl/salsa20_nacl.c
index 7f95c81..2d439ef 100644
--- a/src/crypto/cipher/salsa20/nacl/salsa20_nacl.c
+++ b/src/crypto/cipher/salsa20/nacl/salsa20_nacl.c
@@ -20,6 +20,8 @@
 #include <nacl/crypto_stream_salsa20.h>
 #endif
 
+#include <assert.h>
+
 
 /** The cipher state */
 struct fastd_cipher_state {
@@ -28,7 +30,9 @@ struct fastd_cipher_state {
 
 
 /** Initializes the cipher state */
-static fastd_cipher_state_t *salsa20_init(const uint8_t *key) {
+static fastd_cipher_state_t *salsa20_init(const uint8_t *key, UNUSED int flags) {
+	assert(flags == 0);
+
 	fastd_cipher_state_t *state = fastd_new(fastd_cipher_state_t);
 	memcpy(state->key, key, crypto_stream_salsa20_KEYBYTES);
 
diff --git a/src/crypto/cipher/salsa20/xmm/salsa20_xmm.c b/src/crypto/cipher/salsa20/xmm/salsa20_xmm.c
index dfc1e3a..19cb70f 100644
--- a/src/crypto/cipher/salsa20/xmm/salsa20_xmm.c
+++ b/src/crypto/cipher/salsa20/xmm/salsa20_xmm.c
@@ -18,6 +18,8 @@
 #include "../../../../cpuid.h"
 #include "../../../../crypto.h"
 
+#include <assert.h>
+
 
 /** The length of the key used by Salsa20 */
 #define KEYBYTES 32
@@ -41,7 +43,9 @@ static bool salsa20_available(void) {
 }
 
 /** Initializes the cipher state */
-static fastd_cipher_state_t *salsa20_init(const uint8_t *key) {
+static fastd_cipher_state_t *salsa20_init(const uint8_t *key, UNUSED int flags) {
+	assert(flags == 0);
+
 	fastd_cipher_state_t *state = fastd_new(fastd_cipher_state_t);
 	memcpy(state->key, key, KEYBYTES);
 
diff --git a/src/crypto/cipher/salsa2012/nacl/salsa2012_nacl.c b/src/crypto/cipher/salsa2012/nacl/salsa2012_nacl.c
index be173b6..a897114 100644
--- a/src/crypto/cipher/salsa2012/nacl/salsa2012_nacl.c
+++ b/src/crypto/cipher/salsa2012/nacl/salsa2012_nacl.c
@@ -20,6 +20,8 @@
 #include <nacl/crypto_stream_salsa2012.h>
 #endif
 
+#include <assert.h>
+
 
 /** The cipher state */
 struct fastd_cipher_state {
@@ -28,7 +30,9 @@ struct fastd_cipher_state {
 
 
 /** Initializes the cipher state */
-static fastd_cipher_state_t *salsa2012_init(const uint8_t *key) {
+static fastd_cipher_state_t *salsa2012_init(const uint8_t *key, UNUSED int flags) {
+	assert(flags == 0);
+
 	fastd_cipher_state_t *state = fastd_new(fastd_cipher_state_t);
 	memcpy(state->key, key, crypto_stream_salsa2012_KEYBYTES);
 
diff --git a/src/crypto/cipher/salsa2012/xmm/salsa2012_xmm.c b/src/crypto/cipher/salsa2012/xmm/salsa2012_xmm.c
index eac032d..3e4cf02 100644
--- a/src/crypto/cipher/salsa2012/xmm/salsa2012_xmm.c
+++ b/src/crypto/cipher/salsa2012/xmm/salsa2012_xmm.c
@@ -18,6 +18,8 @@
 #include "../../../../cpuid.h"
 #include "../../../../crypto.h"
 
+#include <assert.h>
+
 
 /** The length of the key used by Salsa20/12 */
 #define KEYBYTES 32
@@ -41,7 +43,9 @@ static bool salsa2012_available(void) {
 }
 
 /** Initializes the cipher state */
-static fastd_cipher_state_t *salsa2012_init(const uint8_t *key) {
+static fastd_cipher_state_t *salsa2012_init(const uint8_t *key, UNUSED int flags) {
+	assert(flags == 0);
+
 	fastd_cipher_state_t *state = fastd_new(fastd_cipher_state_t);
 	memcpy(state->key, key, KEYBYTES);
 
diff --git a/src/crypto/mac/ghash/builtin/ghash_builtin.c b/src/crypto/mac/ghash/builtin/ghash_builtin.c
index c839616..1498a90 100644
--- a/src/crypto/mac/ghash/builtin/ghash_builtin.c
+++ b/src/crypto/mac/ghash/builtin/ghash_builtin.c
@@ -14,6 +14,8 @@
 #include "../../../../alloc.h"
 #include "../../../../crypto.h"
 
+#include <assert.h>
+
 
 /** MAC state used by this GHASH implmentation */
 struct fastd_mac_state {
@@ -54,7 +56,9 @@ static inline void mulH_a(fastd_block128_t *x, const fastd_mac_state_t *cstate)
 
 
 /** Initializes the MAC state with the unpacked key data */
-static fastd_mac_state_t *ghash_init(const uint8_t *key) {
+static fastd_mac_state_t *ghash_init(const uint8_t *key, UNUSED int flags) {
+	assert(flags == 0);
+
 	fastd_mac_state_t *state = fastd_new_aligned(fastd_mac_state_t, 16);
 
 	fastd_block128_t Hbase[4];
diff --git a/src/crypto/mac/ghash/pclmulqdq/ghash_pclmulqdq.h b/src/crypto/mac/ghash/pclmulqdq/ghash_pclmulqdq.h
index 271ba3b..89d2a96 100644
--- a/src/crypto/mac/ghash/pclmulqdq/ghash_pclmulqdq.h
+++ b/src/crypto/mac/ghash/pclmulqdq/ghash_pclmulqdq.h
@@ -16,7 +16,7 @@
 #include "../../../../crypto.h"
 
 
-fastd_mac_state_t *fastd_ghash_pclmulqdq_init(const uint8_t *key);
+fastd_mac_state_t *fastd_ghash_pclmulqdq_init(const uint8_t *key, int flags);
 bool fastd_ghash_pclmulqdq_digest(
 	const fastd_mac_state_t *state, fastd_block128_t *out, const fastd_block128_t *in, size_t length);
 void fastd_ghash_pclmulqdq_free(fastd_mac_state_t *state);
diff --git a/src/crypto/mac/ghash/pclmulqdq/ghash_pclmulqdq_impl.c b/src/crypto/mac/ghash/pclmulqdq/ghash_pclmulqdq_impl.c
index 14bb75c..072f0f2 100644
--- a/src/crypto/mac/ghash/pclmulqdq/ghash_pclmulqdq_impl.c
+++ b/src/crypto/mac/ghash/pclmulqdq/ghash_pclmulqdq_impl.c
@@ -14,6 +14,8 @@
 #include "../../../../alloc.h"
 #include "ghash_pclmulqdq.h"
 
+#include <assert.h>
+
 #include <emmintrin.h>
 #include <tmmintrin.h>
 #include <wmmintrin.h>
@@ -59,7 +61,9 @@ static inline __m128i byteswap(__m128i v) {
 
 
 /** Initializes the state used by this GHASH implementation */
-fastd_mac_state_t *fastd_ghash_pclmulqdq_init(const uint8_t *key) {
+fastd_mac_state_t *fastd_ghash_pclmulqdq_init(const uint8_t *key, UNUSED int flags) {
+	assert(flags == 0);
+
 	fastd_mac_state_t *state = fastd_new_aligned(fastd_mac_state_t, 16);
 
 	memcpy(&state->H, key, sizeof(__m128i));
diff --git a/src/crypto/mac/uhash/builtin/uhash_builtin.c b/src/crypto/mac/uhash/builtin/uhash_builtin.c
index d21ee37..b127e62 100644
--- a/src/crypto/mac/uhash/builtin/uhash_builtin.c
+++ b/src/crypto/mac/uhash/builtin/uhash_builtin.c
@@ -16,6 +16,8 @@
 #include "../../../../log.h"
 #include "../../../../util.h"
 
+#include <assert.h>
+
 
 /** MAC state used by this UHASH implmentation */
 struct fastd_mac_state {
@@ -78,7 +80,9 @@ static inline uint64_t mod_p36(uint64_t a) {
 
 
 /** Initializes the MAC state with the unpacked key data */
-static fastd_mac_state_t *uhash_init(const uint8_t *key) {
+static fastd_mac_state_t *uhash_init(const uint8_t *key, UNUSED int flags) {
+	assert(flags == 0);
+
 	fastd_mac_state_t *state = fastd_new(fastd_mac_state_t);
 
 	const uint32_t *key32 = (const uint32_t *)key;
diff --git a/src/methods/cipher_test/cipher_test.c b/src/methods/cipher_test/cipher_test.c
index 9bd87ec..61b9001 100644
--- a/src/methods/cipher_test/cipher_test.c
+++ b/src/methods/cipher_test/cipher_test.c
@@ -77,7 +77,7 @@ method_session_init(const fastd_method_t *method, const uint8_t *secret, bool in
 	fastd_method_common_init(&session->common, initiator);
 	session->method = method;
 	session->cipher = fastd_cipher_get(method->cipher_info);
-	session->cipher_state = session->cipher->init(secret);
+	session->cipher_state = session->cipher->init(secret, 0);
 
 	pr_warn("using cipher-test method; this method must be used for testing and benchmarks only");
 
diff --git a/src/methods/composed_gmac/composed_gmac.c b/src/methods/composed_gmac/composed_gmac.c
index 2f545d6..0cbb2b5 100644
--- a/src/methods/composed_gmac/composed_gmac.c
+++ b/src/methods/composed_gmac/composed_gmac.c
@@ -120,10 +120,10 @@ method_session_init(const fastd_method_t *method, const uint8_t *secret, bool in
 	session->method = method;
 
 	session->cipher = fastd_cipher_get(method->cipher_info);
-	session->cipher_state = session->cipher->init(secret);
+	session->cipher_state = session->cipher->init(secret, 0);
 
 	session->gmac_cipher = fastd_cipher_get(method->gmac_cipher_info);
-	session->gmac_cipher_state = session->gmac_cipher->init(secret + method->cipher_info->key_length);
+	session->gmac_cipher_state = session->gmac_cipher->init(secret + method->cipher_info->key_length, 0);
 
 	fastd_block128_t H;
 
@@ -141,7 +141,7 @@ method_session_init(const fastd_method_t *method, const uint8_t *secret, bool in
 	}
 
 	session->ghash = fastd_mac_get(method->ghash_info);
-	session->ghash_state = session->ghash->init(H.b);
+	session->ghash_state = session->ghash->init(H.b, 0);
 
 	return session;
 }
diff --git a/src/methods/composed_umac/composed_umac.c b/src/methods/composed_umac/composed_umac.c
index 7930d76..dbd9670 100644
--- a/src/methods/composed_umac/composed_umac.c
+++ b/src/methods/composed_umac/composed_umac.c
@@ -114,14 +114,14 @@ method_session_init(const fastd_method_t *method, const uint8_t *secret, bool in
 	session->method = method;
 
 	session->cipher = fastd_cipher_get(method->cipher_info);
-	session->cipher_state = session->cipher->init(secret);
+	session->cipher_state = session->cipher->init(secret, 0);
 
 	session->umac_cipher = fastd_cipher_get(method->umac_cipher_info);
-	session->umac_cipher_state = session->umac_cipher->init(secret + method->cipher_info->key_length);
+	session->umac_cipher_state = session->umac_cipher->init(secret + method->cipher_info->key_length, 0);
 
 	session->uhash = fastd_mac_get(method->uhash_info);
-	session->uhash_state =
-		session->uhash->init(secret + method->cipher_info->key_length + method->umac_cipher_info->key_length);
+	session->uhash_state = session->uhash->init(
+		secret + method->cipher_info->key_length + method->umac_cipher_info->key_length, 0);
 
 	return session;
 }
diff --git a/src/methods/generic_gmac/generic_gmac.c b/src/methods/generic_gmac/generic_gmac.c
index 7c31713..68cc6da 100644
--- a/src/methods/generic_gmac/generic_gmac.c
+++ b/src/methods/generic_gmac/generic_gmac.c
@@ -95,7 +95,7 @@ method_session_init(const fastd_method_t *method, const uint8_t *secret, bool in
 	session->method = method;
 
 	session->cipher = fastd_cipher_get(method->cipher_info);
-	session->cipher_state = session->cipher->init(secret);
+	session->cipher_state = session->cipher->init(secret, 0);
 
 	static const fastd_block128_t zeroblock = {};
 	fastd_block128_t H;
@@ -111,7 +111,7 @@ method_session_init(const fastd_method_t *method, const uint8_t *secret, bool in
 	}
 
 	session->ghash = fastd_mac_get(method->ghash_info);
-	session->ghash_state = session->ghash->init(H.b);
+	session->ghash_state = session->ghash->init(H.b, 0);
 
 	return session;
 }
diff --git a/src/methods/generic_poly1305/generic_poly1305.c b/src/methods/generic_poly1305/generic_poly1305.c
index c381146..7af4a58 100644
--- a/src/methods/generic_poly1305/generic_poly1305.c
+++ b/src/methods/generic_poly1305/generic_poly1305.c
@@ -93,7 +93,7 @@ method_session_init(const fastd_method_t *method, const uint8_t *secret, bool in
 	fastd_method_common_init(&session->common, initiator);
 	session->method = method;
 	session->cipher = fastd_cipher_get(session->method->cipher_info);
-	session->cipher_state = session->cipher->init(secret);
+	session->cipher_state = session->cipher->init(secret, 0);
 
 	return session;
 }
diff --git a/src/methods/generic_umac/generic_umac.c b/src/methods/generic_umac/generic_umac.c
index f8f9a69..efbd455 100644
--- a/src/methods/generic_umac/generic_umac.c
+++ b/src/methods/generic_umac/generic_umac.c
@@ -88,10 +88,10 @@ method_session_init(const fastd_method_t *method, const uint8_t *secret, bool in
 	session->method = method;
 
 	session->cipher = fastd_cipher_get(method->cipher_info);
-	session->cipher_state = session->cipher->init(secret);
+	session->cipher_state = session->cipher->init(secret, 0);
 
 	session->uhash = fastd_mac_get(method->uhash_info);
-	session->uhash_state = session->uhash->init(secret + method->cipher_info->key_length);
+	session->uhash_state = session->uhash->init(secret + method->cipher_info->key_length, 0);
 
 	return session;
 }
diff --git a/test/benchmark-uhash.c b/test/benchmark-uhash.c
index 77fa41a..c321a6d 100644
--- a/test/benchmark-uhash.c
+++ b/test/benchmark-uhash.c
@@ -47,7 +47,7 @@ int main(void) {
 		return 77;
 	}
 
-	fastd_mac_state_t *mac_state = fastd_mac_uhash_builtin.init(key);
+	fastd_mac_state_t *mac_state = fastd_mac_uhash_builtin.init(key, 0);
 
 	run_benchmark(mac_state, 100000000, 20);
 	run_benchmark(mac_state, 100000000, 100);
diff --git a/test/test-uhash.c b/test/test-uhash.c
index 35a0111..807ecc3 100644
--- a/test/test-uhash.c
+++ b/test/test-uhash.c
@@ -16,7 +16,7 @@
 #include <cmocka.h>
 
 static int setup(void **state) {
-	fastd_mac_state_t *mac_state = fastd_mac_uhash_builtin.init(key);
+	fastd_mac_state_t *mac_state = fastd_mac_uhash_builtin.init(key, 0);
 	*state = mac_state;
 	return 0;
 }