diff --git a/include/psa/crypto.h b/include/psa/crypto.h
index 3eee382..4a60e67 100644
--- a/include/psa/crypto.h
+++ b/include/psa/crypto.h
@@ -103,6 +103,9 @@
  */
 psa_status_t psa_crypto_init(void);
 
+#define BITS_TO_BYTES(bits) (((bits) + 7) / 8)
+#define BYTES_TO_BITS(bytes) ((bytes) * 8)
+
 /**@}*/
 
 /** \defgroup crypto_types Key and algorithm types
@@ -122,7 +125,8 @@
 #define PSA_KEY_TYPE_ASYMMETRIC_MASK            0x60000000
 #define PSA_KEY_TYPE_ASYMMETRIC_MASK_PUBLIC     0x40000000
 #define PSA_KEY_TYPE_ASYMMETRIC_MASK_KEYPAIR    0x60000000
-#define PSA_KEY_TYPE_ECC_TEST_MASK              0x7fff0000
+#define PSA_KEY_TYPE_ASYMMETRIC_TEST_MASK       0x5fff0000
+#define PSA_KEY_TYPE_RSA_TEST_VALUE             0x40000000
 #define PSA_KEY_TYPE_ECC_TEST_VALUE             0x40010000
 
 #define PSA_KEY_TYPE_IS_VENDOR(type) \
@@ -133,8 +137,10 @@
     (((type) & PSA_KEY_TYPE_ASYMMETRIC_MASK) == PSA_KEY_TYPE_ASYMMETRIC_MASK_PUBLIC)
 #define PSA_KEY_TYPE_IS_KEYPAIR(type) \
     (((type) & PSA_KEY_TYPE_ASYMMETRIC_MASK) == PSA_KEY_TYPE_ASYMMETRIC_MASK_KEYPAIR)
+#define PSA_KEY_TYPE_IS_RSA(type)                                       \
+    (((type) & PSA_KEY_TYPE_ASYMMETRIC_TEST_MASK) == PSA_KEY_TYPE_RSA_TEST_VALUE)
 #define PSA_KEY_TYPE_IS_ECC(type)                                       \
-    (((type) & PSA_KEY_TYPE_ECC_TEST_MASK) == PSA_KEY_TYPE_ECC_TEST_VALUE)
+    (((type) & PSA_KEY_TYPE_ASYMMETRIC_TEST_MASK) == PSA_KEY_TYPE_ECC_TEST_VALUE)
 
 typedef uint32_t psa_algorithm_t;
 
@@ -248,6 +254,41 @@
  */
 
 /**
+ * \brief Maximum ECDSA signature size for a given curve bit size
+ *
+ * \param curve_bits    Curve size in bits
+ * \return              Maximum signature size in bytes
+ *
+ * \note This macro returns a compile-time constant if its argument is one.
+ *
+ * \warning This macro may evaluate its argument multiple times.
+ */
+/*
+ * RFC 4492 page 20:
+ *
+ *     Ecdsa-Sig-Value ::= SEQUENCE {
+ *         r       INTEGER,
+ *         s       INTEGER
+ *     }
+ *
+ * Size is at most
+ *    1 (tag) + 1 (len) + 1 (initial 0) + curve_bytes for each of r and s,
+ *    twice that + 1 (tag) + 2 (len) for the sequence
+ * (assuming curve_bytes is less than 126 for r and s,
+ * and less than 124 (total len <= 255) for the sequence)
+ */
+#define PSA_ECDSA_SIGNATURE_SIZE(curve_bits)                          \
+    ( /*T,L of SEQUENCE*/ ((curve_bits) >= 61 * 8 ? 3 : 2) +          \
+      /*T,L of r,s*/       2 * (((curve_bits) >= 127 * 8 ? 3 : 2) +   \
+      /*V of r,s*/               ((curve_bits) + 8) / 8))
+
+
+#define PSA_ASYMMETRIC_SIGN_OUTPUT_SIZE(key_type, key_bits, alg)        \
+    (PSA_KEY_TYPE_IS_RSA(key_type) ? ((void)alg, BITS_TO_BYTES(key_bits)) : \
+     PSA_KEY_TYPE_IS_ECC(key_type) ? PSA_ECDSA_SIGNATURE_SIZE(key_bits) : \
+     0)
+
+/**
  * \brief Sign a hash or short message with a private key.
  *
  */
diff --git a/tests/suites/test_suite_psa_crypto.data b/tests/suites/test_suite_psa_crypto.data
index 51fbf3a..a2d6b89 100644
--- a/tests/suites/test_suite_psa_crypto.data
+++ b/tests/suites/test_suite_psa_crypto.data
@@ -37,6 +37,24 @@
 #depends_on:MBEDTLS_PK_C:MBEDTLS_PK_PARSE_C:MBEDTLS_ECP_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED
 #import_export:"3077020101042049c9a8c18c4b885638c431cf1df1c994131609b580d4fd43a0cab17db2f13eeea00a06082a8648ce3d030107a144034200047772656f814b399279d5e1f1781fac6f099a3c5ca1b0e35351834b08b65e0b572590cdaf8f769361bcf34acfc11e5e074e8426bdde04be6e653945449617de45":PSA_KEY_TYPE_ECC_NISTP256R1:256:0:PSA_SUCCESS:1
 #
+PSA signature size: RSA keypair, 1024 bits, PKCS#1 v1.5 raw
+signature_size:PSA_KEY_TYPE_RSA_KEYPAIR:1024:PSA_ALG_RSA_PKCS1V15_RAW:128
+
+PSA signature size: RSA public key, 1024 bits, PKCS#1 v1.5 raw
+signature_size:PSA_KEY_TYPE_RSA_PUBLIC_KEY:1024:PSA_ALG_RSA_PKCS1V15_RAW:128
+
+PSA signature size: RSA keypair, 1024 bits, PKCS#1 v1.5 SHA-256
+signature_size:PSA_KEY_TYPE_RSA_KEYPAIR:1024:PSA_ALG_RSA_PKCS1V15(PSA_ALG_SHA_256):128
+
+PSA signature size: RSA keypair, 1024 bits, PSS
+signature_size:PSA_KEY_TYPE_RSA_KEYPAIR:1024:PSA_ALG_RSA_PSS_MGF1:128
+
+PSA signature size: RSA keypair, 1023 bits, PKCS#1 v1.5 raw
+signature_size:PSA_KEY_TYPE_RSA_KEYPAIR:1023:PSA_ALG_RSA_PKCS1V15_RAW:128
+
+PSA signature size: RSA keypair, 1025 bits, PKCS#1 v1.5 raw
+signature_size:PSA_KEY_TYPE_RSA_KEYPAIR:1025:PSA_ALG_RSA_PKCS1V15_RAW:129
+
 PSA sign RSA PKCS#1 v1.5, raw
 depends_on:MBEDTLS_PK_PARSE_C:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15
 sign_deterministic:PSA_KEY_TYPE_RSA_KEYPAIR:"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":PSA_ALG_RSA_PKCS1V15_RAW:"616263":"2c7744983f023ac7bb1c55529d83ed11a76a7898a1bb5ce191375a4aa7495a633d27879ff58eba5a57371c34feb1180e8b850d552476ebb5634df620261992f12ebee9097041dbbea85a42d45b344be5073ceb772ffc604954b9158ba81ec3dc4d9d65e3ab7aa318165f38c36f841f1c69cb1cfa494aa5cbb4d6c0efbafb043a"
diff --git a/tests/suites/test_suite_psa_crypto.function b/tests/suites/test_suite_psa_crypto.function
index 3551570..80a7788 100644
--- a/tests/suites/test_suite_psa_crypto.function
+++ b/tests/suites/test_suite_psa_crypto.function
@@ -134,6 +134,18 @@
 /* END_CASE */
 
 /* BEGIN_CASE */
+void signature_size( int type_arg, int bits, int alg_arg, int expected_size_arg )
+{
+    psa_key_type_t type = type_arg;
+    psa_algorithm_t alg = alg_arg;
+    size_t actual_size = PSA_ASYMMETRIC_SIGN_OUTPUT_SIZE(type, bits, alg);
+    TEST_ASSERT( actual_size == (size_t) expected_size_arg );
+exit:
+    ;
+}
+/* END_CASE */
+
+/* BEGIN_CASE */
 void sign_deterministic( int key_type_arg, char *key_hex,
                          int alg_arg, char *input_hex, char *output_hex )
 {
@@ -142,12 +154,14 @@
     psa_algorithm_t alg = alg_arg;
     unsigned char *key_data = NULL;
     size_t key_size;
+    size_t key_bits;
     unsigned char *input_data = NULL;
     size_t input_size;
     unsigned char *output_data = NULL;
     size_t output_size;
-    unsigned char signature[512];
     size_t signature_length;
+    unsigned char *signature = NULL;
+    size_t signature_size;
 
     key_data = mbedtls_calloc( 1, strlen( key_hex ) / 2 );
     TEST_ASSERT( key_data != NULL );
@@ -163,11 +177,19 @@
 
     TEST_ASSERT( psa_import_key( slot, key_type,
                                  key_data, key_size ) == PSA_SUCCESS );
+    TEST_ASSERT( psa_get_key_information( slot,
+                                          NULL,
+                                          &key_bits ) == PSA_SUCCESS );
+
+    signature_size = PSA_ASYMMETRIC_SIGN_OUTPUT_SIZE( key_type, alg, key_bits );
+    TEST_ASSERT( signature_size != 0 );
+    signature = mbedtls_calloc( 1, signature_size );
+    TEST_ASSERT( signature != NULL );
 
     TEST_ASSERT( psa_asymmetric_sign( slot, alg,
                                       input_data, input_size,
                                       NULL, 0,
-                                      signature, sizeof( signature ),
+                                      signature, signature_size,
                                       &signature_length ) == PSA_SUCCESS );
     TEST_ASSERT( signature_length == output_size );
     TEST_ASSERT( memcmp( signature, output_data, output_size ) == 0 );
@@ -177,6 +199,7 @@
     mbedtls_free( key_data );
     mbedtls_free( input_data );
     mbedtls_free( output_data );
+    mbedtls_free( signature );
     mbedtls_psa_crypto_free( );
 }
 /* END_CASE */