diff --git a/auth.c b/auth.c
index e7f4c0d..ab5db90 100644
--- a/auth.c
+++ b/auth.c
@@ -50,18 +50,16 @@ struct lc_auth_ctx *
 lc_auth_ctx_new(const struct lc_auth_impl *impl)
 {
 	struct lc_auth_ctx	*ctx;
-	void			*arg;
 
 	ctx = malloc(sizeof(*ctx));
 	if (ctx == NULL)
 		return NULL;
-	if (impl->argsz > 0) {
-		arg = malloc(impl->argsz);
-		if (arg == NULL) {
+	if (impl->ctx_new != NULL) {
+		ctx->arg = impl->ctx_new(NULL);
+		if (ctx->arg == NULL) {
 			free(ctx);
 			return NULL;
 		}
-		ctx->arg = arg;
 	} else
 		ctx->arg = NULL;
 	ctx->impl = impl;
@@ -72,7 +70,11 @@ lc_auth_ctx_new(const struct lc_auth_impl *impl)
 void
 lc_auth_ctx_free(struct lc_auth_ctx *ctx)
 {
-	if (ctx != NULL)
-		free(ctx->arg);
-	free(ctx);
+	if (ctx != NULL && ctx->impl != NULL && ctx->impl->ctx_free != NULL)
+		ctx->impl->ctx_free(ctx);
+	else {
+		if (ctx != NULL)
+			free(ctx->arg);
+		free(ctx);
+	}
 }
diff --git a/auth.h b/auth.h
index 71e50f4..c5e6a98 100644
--- a/auth.h
+++ b/auth.h
@@ -19,13 +19,14 @@
 
 
 struct lc_auth_impl {
-	int	(*init)(void *, const uint8_t *, size_t);
-	int	(*update)(void *, const uint8_t *, size_t);
-	int	(*final)(void *, uint8_t *, size_t *);
-	int	(*auth)(const uint8_t *, size_t, uint8_t *, size_t *,
+	int	 (*init)(void *, const uint8_t *, size_t);
+	int	 (*update)(void *, const uint8_t *, size_t);
+	int	 (*final)(void *, uint8_t *, size_t *);
+	int	 (*auth)(const uint8_t *, size_t, uint8_t *, size_t *,
 		    const uint8_t *, size_t);
 
-	size_t	  argsz;
+	void	*(*ctx_new)(const void *);
+	void	 (*ctx_free)(void *);
 };
 
 struct lc_auth_ctx {
diff --git a/auth_poly1305.c b/auth_poly1305.c
index 623022f..9c394fc 100644
--- a/auth_poly1305.c
+++ b/auth_poly1305.c
@@ -14,6 +14,8 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#include <stdlib.h>
+
 #include "lilcrypto.h"
 #include "auth.h"
 #include "auth_poly1305.h"
@@ -151,6 +153,11 @@ poly1305_auth(const uint8_t *key, size_t keylen, uint8_t *out, size_t *outlen,
 	    poly1305_final(&ctx, out, outlen);
 }
 
+static void *
+poly1305_ctx_new(const void *arg)
+{
+	return malloc(sizeof(struct poly1305_ctx));
+}
 
 static struct lc_auth_impl	poly1305_impl = {
 	.init = &poly1305_init,
@@ -158,7 +165,8 @@ static struct lc_auth_impl	poly1305_impl = {
 	.final = &poly1305_final,
 	.auth = &poly1305_auth,
 
-	.argsz = sizeof(struct poly1305_ctx),
+	.ctx_new = &poly1305_ctx_new,
+	.ctx_free = NULL,
 };
 
 const struct lc_auth_impl *
diff --git a/cipher.c b/cipher.c
index 127075b..a2c4a25 100644
--- a/cipher.c
+++ b/cipher.c
@@ -82,18 +82,16 @@ struct lc_cipher_ctx *
 lc_cipher_ctx_new(const struct lc_cipher_impl *impl)
 {
 	struct lc_cipher_ctx	*ctx;
-	void			*arg;
 
 	ctx = malloc(sizeof(*ctx));
 	if (ctx == NULL)
 		return NULL;
-	if (impl->argsz > 0) {
-		arg = malloc(impl->argsz);
-		if (arg == NULL) {
+	if (impl->ctx_new != NULL) {
+		ctx->arg = impl->ctx_new(NULL);
+		if (ctx->arg == NULL) {
 			free(ctx);
 			return NULL;
 		}
-		ctx->arg = arg;
 	} else
 		ctx->arg = NULL;
 	ctx->impl = impl;
@@ -104,7 +102,11 @@ lc_cipher_ctx_new(const struct lc_cipher_impl *impl)
 void
 lc_cipher_ctx_free(struct lc_cipher_ctx *ctx)
 {
-	if (ctx != NULL)
-		free(ctx->arg);
-	free(ctx);
+	if (ctx != NULL && ctx->impl != NULL && ctx->impl->ctx_free != NULL)
+		ctx->impl->ctx_free(ctx);
+	else {
+		if (ctx != NULL)
+			free(ctx->arg);
+		free(ctx);
+	}
 }
diff --git a/cipher.h b/cipher.h
index 73e8a8e..d20c4cb 100644
--- a/cipher.h
+++ b/cipher.h
@@ -19,23 +19,24 @@
 
 
 struct lc_cipher_impl {
-	int	(*encrypt_init)(void *, const uint8_t *, size_t,
+	int	 (*encrypt_init)(void *, const uint8_t *, size_t,
 		    const uint8_t *, size_t);
-	int	(*encrypt_update)(void *, uint8_t *, size_t *, const uint8_t *,
+	int	 (*encrypt_update)(void *, uint8_t *, size_t *, const uint8_t *,
 		    size_t);
-	int	(*encrypt_final)(void *, uint8_t *, size_t *);
-	int	(*encrypt)(const uint8_t *, size_t, const uint8_t *, size_t,
+	int	 (*encrypt_final)(void *, uint8_t *, size_t *);
+	int	 (*encrypt)(const uint8_t *, size_t, const uint8_t *, size_t,
 		    uint8_t *, size_t *, const uint8_t *, size_t);
 
-	int	(*decrypt_init)(void *, const uint8_t *, size_t,
+	int	 (*decrypt_init)(void *, const uint8_t *, size_t,
 		    const uint8_t *, size_t);
-	int	(*decrypt_update)(void *, uint8_t *, size_t *, const uint8_t *,
+	int	 (*decrypt_update)(void *, uint8_t *, size_t *, const uint8_t *,
 		    size_t);
-	int	(*decrypt_final)(void *, uint8_t *, size_t *);
-	int	(*decrypt)(const uint8_t *, size_t, const uint8_t *, size_t,
+	int	 (*decrypt_final)(void *, uint8_t *, size_t *);
+	int	 (*decrypt)(const uint8_t *, size_t, const uint8_t *, size_t,
 		    uint8_t *, size_t *, const uint8_t *, size_t);
 
-	size_t	  argsz;
+	void	*(*ctx_new)(const void *);
+	void	 (*ctx_free)(void *);
 };
 
 struct lc_cipher_ctx {
diff --git a/cipher_chacha20.c b/cipher_chacha20.c
index 31102a4..5e09375 100644
--- a/cipher_chacha20.c
+++ b/cipher_chacha20.c
@@ -15,6 +15,7 @@
  */
 
 #include <limits.h>
+#include <stdlib.h>
 
 #include "lilcrypto.h"
 #include "cipher.h"
@@ -177,6 +178,12 @@ chacha20_x(const uint8_t *key, size_t keylen, const uint8_t *iv, size_t ivlen,
 	return rc;
 }
 
+static void *
+chacha20_ctx_new(const void *arg)
+{
+	return malloc(sizeof(struct chacha20_ctx));
+}
+
 
 static struct lc_cipher_impl	chacha20_impl = {
 	.encrypt_init = &chacha20_x_init,
@@ -189,7 +196,8 @@ static struct lc_cipher_impl	chacha20_impl = {
 	.decrypt_final = &chacha20_x_final,
 	.decrypt = &chacha20_x,
 
-	.argsz = sizeof(struct chacha20_ctx),
+	.ctx_new = &chacha20_ctx_new,
+	.ctx_free = NULL,
 };
 
 const struct lc_cipher_impl *