diff --git a/include/polarssl/ecdsa.h b/include/polarssl/ecdsa.h
index bc1afbb..6dcb283 100644
--- a/include/polarssl/ecdsa.h
+++ b/include/polarssl/ecdsa.h
@@ -84,6 +84,48 @@
                   const ecp_point *Q, const mpi *r, const mpi *s);
 
 /**
+ * \brief           Compute ECDSA signature and write it to buffer
+ *
+ * \param ctx       ECDSA context
+ * \param hash      Message hash
+ * \param hlen      Length of hash
+ * \param sig       Buffer that will hold the signature
+ * \param slen      Length of the signature written
+ * \param f_rng     RNG function
+ * \param p_rng     RNG parameter
+ *
+ * \note            The "sig" buffer must be at least as large as twice the
+ *                  size of the curve used, plus 7 (eg. 71 bytes if a 256-bit
+ *                  curve is used).
+ *
+ * \return          0 if successful,
+ *                  or a POLARSSL_ERR_ECP, POLARSSL_ERR_MPI or
+ *                  POLARSSL_ERR_ASN1 error code
+ */
+int ecdsa_write_signature( ecdsa_context *ctx,
+                           const unsigned char *hash, size_t hlen,
+                           unsigned char *sig, size_t *slen,
+                           int (*f_rng)(void *, unsigned char *, size_t),
+                           void *p_rng );
+
+/**
+ * \brief           Read and verify an ECDSA signature
+ *
+ * \param ctx       ECDSA context
+ * \param hash      Message hash
+ * \param hlen      Size of hash
+ * \param sig       Signature to read and verify
+ * \param slen      Size of sig
+ *
+ * \return          0 if successful,
+ *                  POLARSSL_ERR_ECP_BAD_INPUT_DATA if signature is invalid
+ *                  or a POLARSSL_ERR_ECP or POLARSSL_ERR_MPI error code
+ */
+int ecdsa_read_signature( ecdsa_context *ctx,
+                          const unsigned char *hash, size_t hlen,
+                          const unsigned char *sig, size_t slen );
+
+/**
  * \brief           Initialize context
  *
  * \param ctx       Context to initialize
diff --git a/include/polarssl/ecp.h b/include/polarssl/ecp.h
index 7bd9bd5..2c0009c 100644
--- a/include/polarssl/ecp.h
+++ b/include/polarssl/ecp.h
@@ -126,9 +126,10 @@
 #define POLARSSL_ECP_DP_SECP521R1   25
 
 /**
- * Maximum bit size of the groups (that is, of N)
+ * Maximum size of the groups (that is, of N and P)
  */
-#define POLARSSL_ECP_MAX_N_BITS     521
+#define POLARSSL_ECP_MAX_BITS     521
+#define POLARSSL_ECP_MAX_BYTES    ( ( POLARSSL_ECP_MAX_BITS + 7 ) / 8 )
 
 /*
  * Maximum window size (actually, NAF width) used for point multipliation.
diff --git a/library/ecdsa.c b/library/ecdsa.c
index e87bc65..cf5355c 100644
--- a/library/ecdsa.c
+++ b/library/ecdsa.c
@@ -34,6 +34,7 @@
 #if defined(POLARSSL_ECDSA_C)
 
 #include "polarssl/ecdsa.h"
+#include "polarssl/asn1write.h"
 
 /*
  * Derive a suitable integer for group grp from a buffer of length len
@@ -188,6 +189,91 @@
 }
 
 /*
+ * RFC 4492 page 20:
+ *
+ *     Ecdsa-Sig-Value ::= SEQUENCE {
+ *         r       INTEGER,
+ *         s       INTEGER
+ *     }
+ *
+ * Size is at most
+ *    1 (tag) + 1 (len) + 1 (initial 0) + ECP_MAX_BYTES for each of r and s,
+ *    twice that + 1 (tag) + 2 (len) for the sequence
+ * (assuming ECP_MAX_BYTES is less than 126 for r and s,
+ * and less than 124 (total len <= 255) for the sequence)
+ */
+#if POLARSSL_ECP_MAX_BYTES > 124
+#error "POLARSSL_ECP_MAX_BYTES bigger than expected, please fix MAX_SIG_LEN"
+#endif
+#define MAX_SIG_LEN ( 3 + 2 * ( 2 + POLARSSL_ECP_MAX_BYTES ) )
+
+/*
+ * Compute and write signature
+ */
+int ecdsa_write_signature( ecdsa_context *ctx,
+                           const unsigned char *hash, size_t hlen,
+                           unsigned char *sig, size_t *slen,
+                           int (*f_rng)(void *, unsigned char *, size_t),
+                           void *p_rng )
+{
+    int ret;
+    unsigned char buf[MAX_SIG_LEN];
+    unsigned char *p = buf + MAX_SIG_LEN - 1;
+    size_t len = 0;
+
+    if( ( ret = ecdsa_sign( &ctx->grp, &ctx->r, &ctx->s, &ctx->d,
+                            hash, hlen, f_rng, p_rng ) ) != 0 )
+    {
+        return( ret );
+    }
+
+    ASN1_CHK_ADD( len, asn1_write_mpi( &p, buf, &ctx->s ) );
+    ASN1_CHK_ADD( len, asn1_write_mpi( &p, buf, &ctx->r ) );
+
+    ASN1_CHK_ADD( len, asn1_write_len( &p, buf, len ) );
+    ASN1_CHK_ADD( len, asn1_write_tag( &p, buf,
+                                       ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );
+
+    memcpy( sig, p, len );
+    *slen = len;
+
+    return( 0 );
+}
+
+/*
+ * Read and check signature
+ */
+int ecdsa_read_signature( ecdsa_context *ctx,
+                          const unsigned char *hash, size_t hlen,
+                          const unsigned char *sig, size_t slen )
+{
+    int ret;
+    unsigned char *p = (unsigned char *) sig;
+    const unsigned char *end = sig + slen;
+    size_t len;
+
+    if( ( ret = asn1_get_tag( &p, end, &len,
+                    ASN1_CONSTRUCTED | ASN1_SEQUENCE ) ) != 0 )
+    {
+        return( POLARSSL_ERR_ECP_BAD_INPUT_DATA + ret );
+    }
+
+    if( p + len != end )
+        return( POLARSSL_ERR_ECP_BAD_INPUT_DATA +
+                POLARSSL_ERR_ASN1_LENGTH_MISMATCH );
+
+    if( ( ret = asn1_get_mpi( &p, end, &ctx->r ) ) != 0 ||
+        ( ret = asn1_get_mpi( &p, end, &ctx->s ) ) != 0 )
+        return( POLARSSL_ERR_ECP_BAD_INPUT_DATA + ret );
+
+    if( p != end )
+        return( POLARSSL_ERR_ECP_BAD_INPUT_DATA +
+                POLARSSL_ERR_ASN1_LENGTH_MISMATCH );
+
+    return( ecdsa_verify( &ctx->grp, hash, hlen, &ctx->Q, &ctx->r, &ctx->s ) );
+}
+
+/*
  * Initialize context
  */
 void ecdsa_init( ecdsa_context *ctx )
diff --git a/library/ecp.c b/library/ecp.c
index 1468312..a2d13c4 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -1146,7 +1146,7 @@
  * (that is: grp->nbits / w + 1)
  * Allow p_bits + 1 bits in case M = grp->N + 1 is one bit longer than N.
  */
-#define MAX_NAF_LEN     ( POLARSSL_ECP_MAX_N_BITS / 2 + 1 )
+#define MAX_NAF_LEN     ( POLARSSL_ECP_MAX_BITS / 2 + 1 )
 
 /*
  * Integer multiplication: R = m * P
diff --git a/tests/suites/test_suite_ecdsa.data b/tests/suites/test_suite_ecdsa.data
index 386c8f4..886065f 100644
--- a/tests/suites/test_suite_ecdsa.data
+++ b/tests/suites/test_suite_ecdsa.data
@@ -22,3 +22,17 @@
 ECDSA primitive rfc 4754 p521
 ecdsa_prim_test_vectors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
 
+ECDSA write-read random #1
+ecdsa_write_read_random:POLARSSL_ECP_DP_SECP192R1
+
+ECDSA write-read random #2
+ecdsa_write_read_random:POLARSSL_ECP_DP_SECP224R1
+
+ECDSA write-read random #3
+ecdsa_write_read_random:POLARSSL_ECP_DP_SECP256R1
+
+ECDSA write-read random #4
+ecdsa_write_read_random:POLARSSL_ECP_DP_SECP384R1
+
+ECDSA write-read random #5
+ecdsa_write_read_random:POLARSSL_ECP_DP_SECP521R1
diff --git a/tests/suites/test_suite_ecdsa.function b/tests/suites/test_suite_ecdsa.function
index 5e1ba64..46dd1b3 100644
--- a/tests/suites/test_suite_ecdsa.function
+++ b/tests/suites/test_suite_ecdsa.function
@@ -76,3 +76,63 @@
     mpi_free( &r_check ); mpi_free( &s_check );
 }
 /* END_CASE */
+
+/* BEGIN_CASE */
+void ecdsa_write_read_random( int id )
+{
+    ecdsa_context ctx;
+    rnd_pseudo_info rnd_info;
+    unsigned char hash[66];
+    unsigned char sig[200];
+    size_t sig_len, i;
+
+    ecdsa_init( &ctx );
+    memset( &rnd_info, 0x00, sizeof( rnd_pseudo_info ) );
+    memset( hash, 0, sizeof( hash ) );
+    memset( sig, 0x2a, sizeof( sig ) );
+
+    /* prepare material for signature */
+    TEST_ASSERT( rnd_pseudo_rand( &rnd_info, hash, sizeof( hash ) ) == 0 );
+
+    /* generate signing key */
+    TEST_ASSERT( ecp_use_known_dp( &ctx.grp, id ) == 0 );
+    TEST_ASSERT( ecp_gen_keypair( &ctx.grp, &ctx.d, &ctx.Q,
+                                  &rnd_pseudo_rand, &rnd_info ) == 0 );
+
+    /* generate and write signature, then read and verify it */
+    TEST_ASSERT( ecdsa_write_signature( &ctx, hash, sizeof( hash ),
+                 sig, &sig_len, &rnd_pseudo_rand, &rnd_info ) == 0 );
+    TEST_ASSERT( ecdsa_read_signature( &ctx, hash, sizeof( hash ),
+                 sig, sig_len ) == 0 );
+
+    /* check we didn't write past the announced length */
+    for( i = sig_len; i < sizeof( sig ); i++ )
+        TEST_ASSERT( sig[i] == 0x2a );
+
+    /* try verification with invalid length */
+    TEST_ASSERT( ecdsa_read_signature( &ctx, hash, sizeof( hash ),
+                 sig, sig_len - 1 ) != 0 );
+    TEST_ASSERT( ecdsa_read_signature( &ctx, hash, sizeof( hash ),
+                 sig, sig_len + 1 ) != 0 );
+
+    /* try invalid sequence tag */
+    sig[0]++;
+    TEST_ASSERT( ecdsa_read_signature( &ctx, hash, sizeof( hash ),
+                 sig, sig_len ) != 0 );
+    sig[0]--;
+
+    /* try modifying r */
+    sig[10]++;
+    TEST_ASSERT( ecdsa_read_signature( &ctx, hash, sizeof( hash ),
+                 sig, sig_len ) != 0 );
+    sig[10]--;
+
+    /* try modifying s */
+    sig[sig_len - 1]++;
+    TEST_ASSERT( ecdsa_read_signature( &ctx, hash, sizeof( hash ),
+                 sig, sig_len ) != 0 );
+    sig[sig_len - 1]--;
+
+    ecdsa_free( &ctx );
+}
+/* END_CASE */