diff --git a/library/aesce.c b/library/aesce.c
index f2bdce2..1a0db16 100644
--- a/library/aesce.c
+++ b/library/aesce.c
@@ -300,7 +300,7 @@
          rki + key_len_in_words < rko_end;
          rki += key_len_in_words) {
 
-        size_t iteration = (rki - (uint32_t *) rk) / key_len_in_words;
+        size_t iteration = (size_t) (rki - (uint32_t *) rk) / key_len_in_words;
         uint32_t *rko;
         rko = rki + key_len_in_words;
         rko[0] = aes_rot_word(aes_sub_word(rki[key_len_in_words - 1]));
diff --git a/library/base64.c b/library/base64.c
index a58717d..9677dee 100644
--- a/library/base64.c
+++ b/library/base64.c
@@ -116,7 +116,7 @@
         *p++ = '=';
     }
 
-    *olen = p - dst;
+    *olen = (size_t) (p - dst);
     *p = 0;
 
     return 0;
@@ -225,7 +225,7 @@
         }
     }
 
-    *olen = p - dst;
+    *olen = (size_t) (p - dst);
 
     return 0;
 }
diff --git a/library/bignum.c b/library/bignum.c
index 09ce030..1b7ff58 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -701,7 +701,7 @@
     }
 
     *p++ = '\0';
-    *olen = p - buf;
+    *olen = (size_t) (p - buf);
 
 cleanup:
 
diff --git a/library/debug.c b/library/debug.c
index c7bbd41..a9d58e5 100644
--- a/library/debug.c
+++ b/library/debug.c
@@ -366,7 +366,7 @@
     start = text;
     for (cur = text; *cur != '\0'; cur++) {
         if (*cur == '\n') {
-            size_t len = cur - start + 1;
+            size_t len = (size_t) (cur - start) + 1;
             if (len > DEBUG_BUF_SIZE - 1) {
                 len = DEBUG_BUF_SIZE - 1;
             }
diff --git a/library/dhm.c b/library/dhm.c
index 3daf0c2..e423657 100644
--- a/library/dhm.c
+++ b/library/dhm.c
@@ -51,7 +51,7 @@
     n = ((*p)[0] << 8) | (*p)[1];
     (*p) += 2;
 
-    if ((int) (end - *p) < n) {
+    if ((size_t) (end - *p) < (size_t) n) {
         return MBEDTLS_ERR_DHM_BAD_INPUT_DATA;
     }
 
@@ -257,7 +257,7 @@
     DHM_MPI_EXPORT(&ctx->G, n2);
     DHM_MPI_EXPORT(&ctx->GX, n3);
 
-    *olen = p - output;
+    *olen = (size_t) (p - output);
 
 cleanup:
     if (ret != 0 && ret > -128) {
diff --git a/library/ecdh.c b/library/ecdh.c
index e060b18..52b1617 100644
--- a/library/ecdh.c
+++ b/library/ecdh.c
@@ -363,7 +363,7 @@
                                      const unsigned char *end)
 {
     return mbedtls_ecp_tls_read_point(&ctx->grp, &ctx->Qp, buf,
-                                      end - *buf);
+                                      (size_t) (end - *buf));
 }
 
 /*
@@ -379,7 +379,7 @@
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     mbedtls_ecp_group_id grp_id;
-    if ((ret = mbedtls_ecp_tls_read_group_id(&grp_id, buf, end - *buf))
+    if ((ret = mbedtls_ecp_tls_read_group_id(&grp_id, buf, (size_t) (end - *buf)))
         != 0) {
         return ret;
     }
diff --git a/library/ecjpake.c b/library/ecjpake.c
index fb13a39..cdf5d7e 100644
--- a/library/ecjpake.c
+++ b/library/ecjpake.c
@@ -168,7 +168,7 @@
     }
 
     ret = mbedtls_ecp_point_write_binary(grp, P, pf,
-                                         &len, *p + 4, end - (*p + 4));
+                                         &len, *p + 4, (size_t) (end - (*p + 4)));
     if (ret != 0) {
         return ret;
     }
@@ -226,7 +226,7 @@
 
     /* Compute hash */
     MBEDTLS_MPI_CHK(mbedtls_ecjpake_compute_hash(md_type,
-                                                 buf, p - buf, hash));
+                                                 buf, (size_t) (p - buf), hash));
 
     /* Turn it into an integer mod n */
     MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(h, hash,
@@ -269,7 +269,7 @@
         return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
     }
 
-    MBEDTLS_MPI_CHK(mbedtls_ecp_tls_read_point(grp, &V, p, end - *p));
+    MBEDTLS_MPI_CHK(mbedtls_ecp_tls_read_point(grp, &V, p, (size_t) (end - *p)));
 
     if (end < *p || (size_t) (end - *p) < 1) {
         ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
@@ -346,7 +346,7 @@
 
     /* Write it out */
     MBEDTLS_MPI_CHK(mbedtls_ecp_tls_write_point(grp, &V,
-                                                pf, &len, *p, end - *p));
+                                                pf, &len, *p, (size_t) (end - *p)));
     *p += len;
 
     len = mbedtls_mpi_size(&h);   /* actually r */
@@ -392,7 +392,7 @@
      *     ECSchnorrZKP zkp;
      * } ECJPAKEKeyKP;
      */
-    MBEDTLS_MPI_CHK(mbedtls_ecp_tls_read_point(grp, X, p, end - *p));
+    MBEDTLS_MPI_CHK(mbedtls_ecp_tls_read_point(grp, X, p, (size_t) (end - *p)));
     if (mbedtls_ecp_is_zero(X)) {
         ret = MBEDTLS_ERR_ECP_INVALID_KEY;
         goto cleanup;
@@ -431,7 +431,7 @@
     MBEDTLS_MPI_CHK(mbedtls_ecp_gen_keypair_base((mbedtls_ecp_group *) grp, G, x, X,
                                                  f_rng, p_rng));
     MBEDTLS_MPI_CHK(mbedtls_ecp_tls_write_point(grp, X,
-                                                pf, &len, *p, end - *p));
+                                                pf, &len, *p, (size_t) (end - *p)));
     *p += len;
 
     /* Generate and write proof */
@@ -504,7 +504,7 @@
     MBEDTLS_MPI_CHK(ecjpake_kkp_write(md_type, grp, pf, G, xm2, Xb, id,
                                       &p, end, f_rng, p_rng));
 
-    *olen = p - buf;
+    *olen = (size_t) (p - buf);
 
 cleanup:
     return ret;
@@ -693,7 +693,7 @@
             goto cleanup;
         }
         MBEDTLS_MPI_CHK(mbedtls_ecp_tls_write_group(&ctx->grp, &ec_len,
-                                                    p, end - p));
+                                                    p, (size_t) (end - p)));
         p += ec_len;
     }
 
@@ -702,7 +702,7 @@
         goto cleanup;
     }
     MBEDTLS_MPI_CHK(mbedtls_ecp_tls_write_point(&ctx->grp, &Xm,
-                                                ctx->point_format, &ec_len, p, end - p));
+                                                ctx->point_format, &ec_len, p, (size_t) (end - p)));
     p += ec_len;
 
     MBEDTLS_MPI_CHK(ecjpake_zkp_write(ctx->md_type, &ctx->grp,
@@ -710,7 +710,7 @@
                                       &G, &xm, &Xm, ID_MINE,
                                       &p, end, f_rng, p_rng));
 
-    *olen = p - buf;
+    *olen = (size_t) (p - buf);
 
 cleanup:
     mbedtls_ecp_point_free(&G);
diff --git a/library/lms.c b/library/lms.c
index 0c470a0..00525bb 100644
--- a/library/lms.c
+++ b/library/lms.c
@@ -505,7 +505,7 @@
     unsigned int height;
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
 
-    tree = mbedtls_calloc(MERKLE_TREE_NODE_AM(ctx->params.type),
+    tree = mbedtls_calloc((size_t) MERKLE_TREE_NODE_AM(ctx->params.type),
                           node_bytes);
     if (tree == NULL) {
         return MBEDTLS_ERR_LMS_ALLOC_FAILED;
@@ -530,7 +530,7 @@
 
 exit:
     mbedtls_zeroize_and_free(tree, node_bytes *
-                             MERKLE_TREE_NODE_AM(ctx->params.type));
+                             (size_t) MERKLE_TREE_NODE_AM(ctx->params.type));
 
     return ret;
 }
@@ -669,7 +669,7 @@
         return MBEDTLS_ERR_LMS_BAD_INPUT_DATA;
     }
 
-    tree = mbedtls_calloc(MERKLE_TREE_NODE_AM(priv_ctx->params.type),
+    tree = mbedtls_calloc((size_t) MERKLE_TREE_NODE_AM(priv_ctx->params.type),
                           node_bytes);
     if (tree == NULL) {
         return MBEDTLS_ERR_LMS_ALLOC_FAILED;
@@ -692,7 +692,7 @@
 
 exit:
     mbedtls_zeroize_and_free(tree, node_bytes *
-                             MERKLE_TREE_NODE_AM(priv_ctx->params.type));
+                             (size_t) MERKLE_TREE_NODE_AM(priv_ctx->params.type));
 
     return ret;
 }
diff --git a/library/oid.c b/library/oid.c
index 6184abe..d8339c1 100644
--- a/library/oid.c
+++ b/library/oid.c
@@ -1129,7 +1129,7 @@
         }
     }
 
-    encoded_len = out_ptr - oid->p;
+    encoded_len = (size_t) (out_ptr - oid->p);
     resized_mem = mbedtls_calloc(encoded_len, 1);
     if (resized_mem == NULL) {
         ret = MBEDTLS_ERR_ASN1_ALLOC_FAILED;
diff --git a/library/pem.c b/library/pem.c
index 9500ffc..539134c 100644
--- a/library/pem.c
+++ b/library/pem.c
@@ -298,7 +298,7 @@
     if (*end == '\n') {
         end++;
     }
-    *use_len = end - data;
+    *use_len = (size_t) (end - data);
 
     enc = 0;
 
@@ -383,7 +383,7 @@
         return MBEDTLS_ERR_PEM_INVALID_DATA;
     }
 
-    ret = mbedtls_base64_decode(NULL, 0, &len, s1, s2 - s1);
+    ret = mbedtls_base64_decode(NULL, 0, &len, s1, (size_t) (s2 - s1));
 
     if (ret == MBEDTLS_ERR_BASE64_INVALID_CHARACTER) {
         return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_PEM_INVALID_DATA, ret);
@@ -393,7 +393,7 @@
         return MBEDTLS_ERR_PEM_ALLOC_FAILED;
     }
 
-    if ((ret = mbedtls_base64_decode(buf, len, &len, s1, s2 - s1)) != 0) {
+    if ((ret = mbedtls_base64_decode(buf, len, &len, s1, (size_t) (s2 - s1))) != 0) {
         mbedtls_zeroize_and_free(buf, len);
         return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_PEM_INVALID_DATA, ret);
     }
@@ -508,7 +508,7 @@
     p += strlen(footer);
 
     *p++ = '\0';
-    *olen = p - buf;
+    *olen = (size_t) (p - buf);
 
     /* Clean any remaining data previously written to the buffer */
     memset(buf + *olen, 0, buf_len - *olen);
diff --git a/library/pkcs7.c b/library/pkcs7.c
index 36b49f5..0869c2e 100644
--- a/library/pkcs7.c
+++ b/library/pkcs7.c
@@ -316,7 +316,7 @@
         goto out;
     }
 
-    signer->issuer_raw.len =  *p - signer->issuer_raw.p;
+    signer->issuer_raw.len =  (size_t) (*p - signer->issuer_raw.p);
 
     ret = mbedtls_x509_get_serial(p, end_issuer_and_sn, &signer->serial);
     if (ret != 0) {
diff --git a/library/pkparse.c b/library/pkparse.c
index 3bb5f7b..edebf92 100644
--- a/library/pkparse.c
+++ b/library/pkparse.c
@@ -928,7 +928,7 @@
             ret = pk_use_ecparams(&alg_params, pk);
         }
         if (ret == 0) {
-            ret = pk_ecc_set_pubkey(pk, *p, end - *p);
+            ret = pk_ecc_set_pubkey(pk, *p, (size_t) (end - *p));
             *p += end - *p;
         }
     } else
@@ -1233,7 +1233,7 @@
                                          MBEDTLS_ERR_ASN1_LENGTH_MISMATCH);
             }
 
-            if ((ret = pk_ecc_set_pubkey(pk, p, end2 - p)) == 0) {
+            if ((ret = pk_ecc_set_pubkey(pk, p, (size_t) (end2 - p))) == 0) {
                 pubkey_done = 1;
             } else {
                 /*
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index bbd6b24..0684014 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -6625,7 +6625,7 @@
     memcpy(cur, data, data_length);
     cur += data_length;
 
-    status = psa_tls12_prf_set_key(prf, pms, cur - pms);
+    status = psa_tls12_prf_set_key(prf, pms, (size_t) (cur - pms));
 
     mbedtls_zeroize_and_free(pms, pms_len);
     return status;
diff --git a/library/rsa.c b/library/rsa.c
index 38c3dd6..1bf5d13 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -1620,12 +1620,12 @@
         goto cleanup;
     }
 
-    if (ilen - (p - buf) > output_max_len) {
+    if (ilen - ((size_t) (p - buf)) > output_max_len) {
         ret = MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE;
         goto cleanup;
     }
 
-    *olen = ilen - (p - buf);
+    *olen = ilen - ((size_t) (p - buf));
     if (*olen != 0) {
         memcpy(output, p, *olen);
     }
@@ -2191,7 +2191,7 @@
         return MBEDTLS_ERR_RSA_INVALID_PADDING;
     }
 
-    observed_salt_len = hash_start - p;
+    observed_salt_len = (size_t) (hash_start - p);
 
     if (expected_salt_len != MBEDTLS_RSA_SALT_LEN_ANY &&
         observed_salt_len != (size_t) expected_salt_len) {
diff --git a/library/ssl_client.c b/library/ssl_client.c
index 0e87d86..7284ee2 100644
--- a/library/ssl_client.c
+++ b/library/ssl_client.c
@@ -155,7 +155,7 @@
         p += protocol_name_len;
     }
 
-    *out_len = p - buf;
+    *out_len = (size_t) (p - buf);
 
     /* List length = *out_len - 2 (ext_type) - 2 (ext_len) - 2 (list_len) */
     MBEDTLS_PUT_UINT16_BE(*out_len - 6, buf, 4);
@@ -285,7 +285,7 @@
     }
 
     /* Length of named_group_list */
-    named_group_list_len = p - named_group_list;
+    named_group_list_len = (size_t) (p - named_group_list);
     if (named_group_list_len == 0) {
         MBEDTLS_SSL_DEBUG_MSG(1, ("No group available."));
         return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
@@ -301,7 +301,7 @@
     MBEDTLS_SSL_DEBUG_BUF(3, "Supported groups extension",
                           buf + 4, named_group_list_len + 2);
 
-    *out_len = p - buf;
+    *out_len = (size_t) (p - buf);
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1_3)
     mbedtls_ssl_tls13_set_hs_sent_ext_mask(
@@ -391,14 +391,14 @@
     }
 
     /* Write the cipher_suites length in number of bytes */
-    cipher_suites_len = p - cipher_suites;
+    cipher_suites_len = (size_t) (p - cipher_suites);
     MBEDTLS_PUT_UINT16_BE(cipher_suites_len, buf, 0);
     MBEDTLS_SSL_DEBUG_MSG(3,
                           ("client hello, got %" MBEDTLS_PRINTF_SIZET " cipher suites",
                            cipher_suites_len/2));
 
     /* Output the total length of cipher_suites field. */
-    *out_len = p - buf;
+    *out_len = (size_t) (p - buf);
 
     return 0;
 }
@@ -679,7 +679,7 @@
 #endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED */
 
     /* Write the length of the list of extensions. */
-    extensions_len = p - p_extensions_len - 2;
+    extensions_len = (size_t) (p - p_extensions_len) - 2;
 
     if (extensions_len == 0) {
         p = p_extensions_len;
@@ -696,7 +696,7 @@
         3, MBEDTLS_SSL_HS_CLIENT_HELLO, handshake->sent_extensions);
 #endif
 
-    *out_len = p - buf;
+    *out_len = (size_t) (p - buf);
     return 0;
 }
 
diff --git a/library/ssl_msg.c b/library/ssl_msg.c
index cffd1c9..0d71884 100644
--- a/library/ssl_msg.c
+++ b/library/ssl_msg.c
@@ -848,7 +848,7 @@
         cur += 2;
     }
 
-    *add_data_len = cur - add_data;
+    *add_data_len = (size_t) (cur - add_data);
 }
 
 #if defined(MBEDTLS_SSL_HAVE_AEAD)
@@ -1212,7 +1212,7 @@
                                                    iv, transform->ivlen,
                                                    add_data, add_data_len,
                                                    data, rec->data_len, /* src */
-                                                   data, rec->buf_len - (data - rec->buf), /* dst */
+                                                   data, rec->buf_len - (size_t) (data - rec->buf), /* dst */
                                                    &rec->data_len,
                                                    transform->taglen)) != 0) {
             MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_cipher_auth_encrypt_ext", ret);
@@ -1635,12 +1635,13 @@
             return ret;
         }
 #else
-        if ((ret = mbedtls_cipher_auth_decrypt_ext(&transform->cipher_ctx_dec,
-                                                   iv, transform->ivlen,
-                                                   add_data, add_data_len,
-                                                   data, rec->data_len + transform->taglen, /* src */
-                                                   data, rec->buf_len - (data - rec->buf), &olen, /* dst */
-                                                   transform->taglen)) != 0) {
+        if ((ret = mbedtls_cipher_auth_decrypt_ext
+                       (&transform->cipher_ctx_dec,
+                       iv, transform->ivlen,
+                       add_data, add_data_len,
+                       data, rec->data_len + transform->taglen, /* src */
+                       data, rec->buf_len - (size_t) (data - rec->buf), &olen, /* dst */
+                       transform->taglen)) != 0) {
             MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_cipher_auth_decrypt_ext", ret);
 
             if (ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED) {
@@ -2228,7 +2229,7 @@
             MBEDTLS_SSL_DEBUG_MSG(2, ("timer has expired"));
             ret = MBEDTLS_ERR_SSL_TIMEOUT;
         } else {
-            len = in_buf_len - (ssl->in_hdr - ssl->in_buf);
+            len = in_buf_len - (size_t) (ssl->in_hdr - ssl->in_buf);
 
             if (mbedtls_ssl_is_handshake_over(ssl) == 0) {
                 timeout = ssl->handshake->retransmit_timeout;
@@ -2592,7 +2593,7 @@
         } else {
             const unsigned char * const p = ssl->handshake->cur_msg_p;
             const size_t hs_len = cur->len - 12;
-            const size_t frag_off = p - (cur->p + 12);
+            const size_t frag_off = (size_t) (p - (cur->p + 12));
             const size_t rem_len = hs_len - frag_off;
             size_t cur_hs_frag_len, max_hs_frag_len;
 
@@ -2969,9 +2970,9 @@
             mbedtls_record rec;
 
             rec.buf         = ssl->out_iv;
-            rec.buf_len     = out_buf_len - (ssl->out_iv - ssl->out_buf);
+            rec.buf_len     = out_buf_len - (size_t) (ssl->out_iv - ssl->out_buf);
             rec.data_len    = ssl->out_msglen;
-            rec.data_offset = ssl->out_msg - rec.buf;
+            rec.data_offset = (size_t) (ssl->out_msg - rec.buf);
 
             memcpy(&rec.ctr[0], ssl->out_ctr, sizeof(rec.ctr));
             mbedtls_ssl_write_version(rec.ver, ssl->conf->transport, tls_ver);
@@ -3594,7 +3595,7 @@
         return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
     }
 
-    *olen = p - obuf;
+    *olen = (size_t) (p - obuf);
 
     /* Go back and fill length fields */
     obuf[27] = (unsigned char) (*olen - 28);
diff --git a/library/ssl_ticket.c b/library/ssl_ticket.c
index 61c87be..0908982 100644
--- a/library/ssl_ticket.c
+++ b/library/ssl_ticket.c
@@ -341,7 +341,7 @@
 
     /* Dump session state */
     if ((ret = mbedtls_ssl_session_save(session,
-                                        state, end - state,
+                                        state, (size_t) (end - state),
                                         &clear_len)) != 0 ||
         (unsigned long) clear_len > 65535) {
         goto cleanup;
@@ -364,7 +364,7 @@
                                                /* Additional data: key name, IV and length */
                                                key_name, TICKET_ADD_DATA_LEN,
                                                state, clear_len,
-                                               state, end - state, &ciph_len,
+                                               state, (size_t) (end - state), &ciph_len,
                                                TICKET_AUTH_TAG_BYTES)) != 0) {
         goto cleanup;
     }
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 944caa0..50f3a61 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -3755,7 +3755,7 @@
     session->tls_version = (mbedtls_ssl_protocol_version) (0x0300 | *p++);
 
     /* Dispatch according to TLS version. */
-    remaining_len = (end - p);
+    remaining_len = (size_t) (end - p);
     switch (session->tls_version) {
 #if defined(MBEDTLS_SSL_PROTO_TLS1_2)
         case MBEDTLS_SSL_VERSION_TLS1_2:
@@ -6795,7 +6795,7 @@
 
         /* Write length only when we know the actual value */
         if ((ret = mbedtls_dhm_calc_secret(&ssl->handshake->dhm_ctx,
-                                           p + 2, end - (p + 2), &len,
+                                           p + 2, (size_t) (end - (p + 2)), &len,
                                            ssl->conf->f_rng, ssl->conf->p_rng)) != 0) {
             MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_dhm_calc_secret", ret);
             return ret;
@@ -6812,7 +6812,7 @@
         size_t zlen;
 
         if ((ret = mbedtls_ecdh_calc_secret(&ssl->handshake->ecdh_ctx, &zlen,
-                                            p + 2, end - (p + 2),
+                                            p + 2, (size_t) (end - (p + 2)),
                                             ssl->conf->f_rng, ssl->conf->p_rng)) != 0) {
             MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ecdh_calc_secret", ret);
             return ret;
@@ -6845,7 +6845,7 @@
     memcpy(p, psk, psk_len);
     p += psk_len;
 
-    ssl->handshake->pmslen = p - ssl->handshake->premaster;
+    ssl->handshake->pmslen = (size_t) (p - ssl->handshake->premaster);
 
     return 0;
 }
@@ -9328,7 +9328,7 @@
     }
 
     /* Length of supported_signature_algorithms */
-    supported_sig_alg_len = p - supported_sig_alg;
+    supported_sig_alg_len = (size_t) (p - supported_sig_alg);
     if (supported_sig_alg_len == 0) {
         MBEDTLS_SSL_DEBUG_MSG(1, ("No signature algorithms defined."));
         return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
@@ -9338,7 +9338,7 @@
     MBEDTLS_PUT_UINT16_BE(supported_sig_alg_len + 2, buf, 2);
     MBEDTLS_PUT_UINT16_BE(supported_sig_alg_len, buf, 4);
 
-    *out_len = p - buf;
+    *out_len = (size_t) (p - buf);
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1_3)
     mbedtls_ssl_tls13_set_hs_sent_ext_mask(ssl, MBEDTLS_TLS_EXT_SIG_ALG);
diff --git a/library/ssl_tls12_client.c b/library/ssl_tls12_client.c
index 9aa46bd..78297e8 100644
--- a/library/ssl_tls12_client.c
+++ b/library/ssl_tls12_client.c
@@ -607,7 +607,7 @@
     p += ext_len;
 #endif
 
-    *out_len = p - buf;
+    *out_len = (size_t) (p - buf);
 
     return 0;
 }
@@ -2174,7 +2174,7 @@
 #endif
     p   = ssl->in_msg + mbedtls_ssl_hs_hdr_len(ssl);
     end = ssl->in_msg + ssl->in_hslen;
-    MBEDTLS_SSL_DEBUG_BUF(3,   "server key exchange", p, end - p);
+    MBEDTLS_SSL_DEBUG_BUF(3,   "server key exchange", p, (size_t) (end - p));
 
 #if defined(MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED)
     if (ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_PSK ||
@@ -2299,7 +2299,7 @@
         mbedtls_md_type_t md_alg = MBEDTLS_MD_NONE;
         mbedtls_pk_type_t pk_alg = MBEDTLS_PK_NONE;
         unsigned char *params = ssl->in_msg + mbedtls_ssl_hs_hdr_len(ssl);
-        size_t params_len = p - params;
+        size_t params_len = (size_t) (p - params);
         void *rs_ctx = NULL;
         uint16_t sig_alg;
 
@@ -3252,9 +3252,9 @@
     size_t hashlen;
     void *rs_ctx = NULL;
 #if defined(MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH)
-    size_t out_buf_len = ssl->out_buf_len - (ssl->out_msg - ssl->out_buf);
+    size_t out_buf_len = ssl->out_buf_len - (size_t) (ssl->out_msg - ssl->out_buf);
 #else
-    size_t out_buf_len = MBEDTLS_SSL_OUT_BUFFER_LEN - (ssl->out_msg - ssl->out_buf);
+    size_t out_buf_len = MBEDTLS_SSL_OUT_BUFFER_LEN - (size_t) (ssl->out_msg - ssl->out_buf);
 #endif
 
     MBEDTLS_SSL_DEBUG_MSG(2, ("=> write certificate verify"));
diff --git a/library/ssl_tls12_server.c b/library/ssl_tls12_server.c
index b007e5c..c2e0814 100644
--- a/library/ssl_tls12_server.c
+++ b/library/ssl_tls12_server.c
@@ -1858,7 +1858,7 @@
         *p++ = 0x00;
     }
 
-    *olen = p - buf;
+    *olen = (size_t) (p - buf);
 }
 
 #if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
@@ -1950,7 +1950,7 @@
 
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
     ret = mbedtls_psa_ecjpake_write_round(&ssl->handshake->psa_pake_ctx,
-                                          p + 2, end - p - 2, &kkpp_len,
+                                          p + 2, (size_t) (end - p - 2), &kkpp_len,
                                           MBEDTLS_ECJPAKE_ROUND_ONE);
     if (ret != 0) {
         psa_destroy_key(ssl->handshake->psa_pake_password);
@@ -1960,7 +1960,7 @@
     }
 #else
     ret = mbedtls_ecjpake_write_round_one(&ssl->handshake->ecjpake_ctx,
-                                          p + 2, end - p - 2, &kkpp_len,
+                                          p + 2, (size_t) (end - p - 2), &kkpp_len,
                                           ssl->conf->f_rng, ssl->conf->p_rng);
     if (ret != 0) {
         MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ecjpake_write_round_one", ret);
@@ -2081,7 +2081,7 @@
 
     MBEDTLS_SSL_DEBUG_BUF(3, "cookie sent", cookie_len_byte + 1, *cookie_len_byte);
 
-    ssl->out_msglen  = p - ssl->out_msg;
+    ssl->out_msglen  = (size_t) (p - ssl->out_msg);
     ssl->out_msgtype = MBEDTLS_SSL_MSG_HANDSHAKE;
     ssl->out_msg[0]  = MBEDTLS_SSL_HS_HELLO_VERIFY_REQUEST;
 
@@ -2386,7 +2386,7 @@
         p += 2 + ext_len;
     }
 
-    ssl->out_msglen  = p - buf;
+    ssl->out_msglen  = (size_t) (p - buf);
     ssl->out_msgtype = MBEDTLS_SSL_MSG_HANDSHAKE;
     ssl->out_msg[0]  = MBEDTLS_SSL_HS_SERVER_HELLO;
 
@@ -2570,12 +2570,12 @@
 
             MBEDTLS_SSL_DEBUG_BUF(3, "requested DN", p - dn_size, dn_size);
 
-            total_dn_size += 2 + dn_size;
+            total_dn_size += (unsigned short) (2 + dn_size);
             crt = crt->next;
         }
     }
 
-    ssl->out_msglen  = p - buf;
+    ssl->out_msglen  = (size_t) (p - buf);
     ssl->out_msgtype = MBEDTLS_SSL_MSG_HANDSHAKE;
     ssl->out_msg[0]  = MBEDTLS_SSL_HS_CERTIFICATE_REQUEST;
     MBEDTLS_PUT_UINT16_BE(total_dn_size, ssl->out_msg, 4 + ct_len + sa_len);
@@ -2779,9 +2779,9 @@
 
 #if defined(MBEDTLS_KEY_EXCHANGE_WITH_SERVER_SIGNATURE_ENABLED)
 #if defined(MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH)
-    size_t out_buf_len = ssl->out_buf_len - (ssl->out_msg - ssl->out_buf);
+    size_t out_buf_len = ssl->out_buf_len - (size_t) (ssl->out_msg - ssl->out_buf);
 #else
-    size_t out_buf_len = MBEDTLS_SSL_OUT_BUFFER_LEN - (ssl->out_msg - ssl->out_buf);
+    size_t out_buf_len = MBEDTLS_SSL_OUT_BUFFER_LEN - (size_t) (ssl->out_msg - ssl->out_buf);
 #endif
 #endif
 
@@ -3086,7 +3086,7 @@
             return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
         }
 
-        size_t dig_signed_len = ssl->out_msg + ssl->out_msglen - dig_signed;
+        size_t dig_signed_len = (size_t) (ssl->out_msg + ssl->out_msglen - dig_signed);
         size_t hashlen = 0;
         unsigned char hash[MBEDTLS_MD_MAX_SIZE];
 
@@ -3763,7 +3763,7 @@
         handshake->xxdh_psa_privkey = MBEDTLS_SVC_KEY_ID_INIT;
 #else
         if ((ret = mbedtls_ecdh_read_public(&ssl->handshake->ecdh_ctx,
-                                            p, end - p)) != 0) {
+                                            p, (size_t) (end - p))) != 0) {
             MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ecdh_read_public", ret);
             return MBEDTLS_ERR_SSL_DECODE_ERROR;
         }
@@ -3976,7 +3976,7 @@
         }
 
         if ((ret = mbedtls_ecdh_read_public(&ssl->handshake->ecdh_ctx,
-                                            p, end - p)) != 0) {
+                                            p, (size_t) (end - p))) != 0) {
             MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ecdh_read_public", ret);
             return MBEDTLS_ERR_SSL_DECODE_ERROR;
         }
@@ -4005,7 +4005,7 @@
     if (ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECJPAKE) {
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
         if ((ret = mbedtls_psa_ecjpake_read_round(
-                 &ssl->handshake->psa_pake_ctx, p, end - p,
+                 &ssl->handshake->psa_pake_ctx, p, (size_t) (end - p),
                  MBEDTLS_ECJPAKE_ROUND_TWO)) != 0) {
             psa_destroy_key(ssl->handshake->psa_pake_password);
             psa_pake_abort(&ssl->handshake->psa_pake_ctx);
@@ -4015,7 +4015,7 @@
         }
 #else
         ret = mbedtls_ecjpake_read_round_two(&ssl->handshake->ecjpake_ctx,
-                                             p, end - p);
+                                             p, (size_t) (end - p));
         if (ret != 0) {
             MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ecjpake_read_round_two", ret);
             return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
diff --git a/library/x509_create.c b/library/x509_create.c
index 424cce1..8f31c3b 100644
--- a/library/x509_create.c
+++ b/library/x509_create.c
@@ -169,7 +169,7 @@
             return MBEDTLS_ERR_X509_INVALID_NAME;
         }
     }
-    *data_len = d - data;
+    *data_len = (size_t) (d - data);
     return 0;
 }
 
@@ -297,8 +297,8 @@
 
     while (c <= end) {
         if (in_attr_type && *c == '=') {
-            if ((attr_descr = x509_attr_descr_from_name(s, c - s)) == NULL) {
-                if ((mbedtls_oid_from_numeric_string(&oid, s, c - s)) != 0) {
+            if ((attr_descr = x509_attr_descr_from_name(s, (size_t) (c - s))) == NULL) {
+                if ((mbedtls_oid_from_numeric_string(&oid, s, (size_t) (c - s))) != 0) {
                     return MBEDTLS_ERR_X509_INVALID_NAME;
                 } else {
                     numericoid = 1;
@@ -322,7 +322,7 @@
                 /* We know that c >= s (loop invariant) and c != s (in this
                  * else branch), hence c - s - 1 >= 0. */
                 parse_ret = parse_attribute_value_hex_der_encoded(
-                    s + 1, c - s - 1,
+                    s + 1, (size_t) (c - s) - 1,
                     data, sizeof(data), &data_len, &tag);
                 if (parse_ret != 0) {
                     mbedtls_free(oid.p);
diff --git a/library/x509_crl.c b/library/x509_crl.c
index cad784e..fdbad23 100644
--- a/library/x509_crl.c
+++ b/library/x509_crl.c
@@ -367,7 +367,7 @@
     }
 
     end = p + len;
-    crl->tbs.len = end - crl->tbs.p;
+    crl->tbs.len = (size_t) (end - crl->tbs.p);
 
     /*
      * Version  ::=  INTEGER  OPTIONAL {  v1(0), v2(1)  }
@@ -411,7 +411,7 @@
         return ret;
     }
 
-    crl->issuer_raw.len = p - crl->issuer_raw.p;
+    crl->issuer_raw.len = (size_t) (p - crl->issuer_raw.p);
 
     /*
      * thisUpdate          Time
diff --git a/library/x509_crt.c b/library/x509_crt.c
index f41eb47..1fe4448 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -1108,7 +1108,7 @@
     }
 
     end = crt_end = p + len;
-    crt->raw.len = crt_end - buf;
+    crt->raw.len = (size_t) (crt_end - buf);
     if (make_copy != 0) {
         /* Create and populate a new buffer for the raw field. */
         crt->raw.p = p = mbedtls_calloc(1, crt->raw.len);
@@ -1138,7 +1138,7 @@
     }
 
     end = p + len;
-    crt->tbs.len = end - crt->tbs.p;
+    crt->tbs.len = (size_t) (end - crt->tbs.p);
 
     /*
      * Version  ::=  INTEGER  {  v1(0), v2(1), v3(2)  }
@@ -1185,7 +1185,7 @@
         return ret;
     }
 
-    crt->issuer_raw.len = p - crt->issuer_raw.p;
+    crt->issuer_raw.len = (size_t) (p - crt->issuer_raw.p);
 
     /*
      * Validity ::= SEQUENCE {
@@ -1215,7 +1215,7 @@
         return ret;
     }
 
-    crt->subject_raw.len = p - crt->subject_raw.p;
+    crt->subject_raw.len = (size_t) (p - crt->subject_raw.p);
 
     /*
      * SubjectPublicKeyInfo
@@ -1225,7 +1225,7 @@
         mbedtls_x509_crt_free(crt);
         return ret;
     }
-    crt->pk_raw.len = p - crt->pk_raw.p;
+    crt->pk_raw.len = (size_t) (p - crt->pk_raw.p);
 
     /*
      *  issuerUniqueID  [1]  IMPLICIT UniqueIdentifier OPTIONAL,
diff --git a/library/x509_csr.c b/library/x509_csr.c
index a293ec0..79b1589 100644
--- a/library/x509_csr.c
+++ b/library/x509_csr.c
@@ -328,7 +328,7 @@
     }
 
     end = p + len;
-    csr->cri.len = end - csr->cri.p;
+    csr->cri.len = (size_t) (end - csr->cri.p);
 
     /*
      *  Version  ::=  INTEGER {  v1(0) }
@@ -361,7 +361,7 @@
         return ret;
     }
 
-    csr->subject_raw.len = p - csr->subject_raw.p;
+    csr->subject_raw.len = (size_t) (p - csr->subject_raw.p);
 
     /*
      *  subjectPKInfo SubjectPublicKeyInfo
diff --git a/library/x509write_crt.c b/library/x509write_crt.c
index 4c019ee..44b6b17 100644
--- a/library/x509write_crt.c
+++ b/library/x509write_crt.c
@@ -481,7 +481,7 @@
      */
     MBEDTLS_ASN1_CHK_ADD(pub_len,
                          mbedtls_pk_write_pubkey_der(ctx->subject_key,
-                                                     buf, c - buf));
+                                                     buf, (size_t) (c - buf)));
     c -= pub_len;
     len += pub_len;
 
diff --git a/library/x509write_csr.c b/library/x509write_csr.c
index 4e39755..254da69 100644
--- a/library/x509write_csr.c
+++ b/library/x509write_csr.c
@@ -185,7 +185,7 @@
                              MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_CONTEXT_SPECIFIC));
 
     MBEDTLS_ASN1_CHK_ADD(pub_len, mbedtls_pk_write_pubkey_der(ctx->key,
-                                                              buf, c - buf));
+                                                              buf, (size_t) (c - buf)));
     c -= pub_len;
     len += pub_len;
 
@@ -276,7 +276,7 @@
                              MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));
 
     /* Zero the unused bytes at the start of buf */
-    memset(buf, 0, c2 - buf);
+    memset(buf, 0, (size_t) (c2 - buf));
 
     return (int) len;
 }