diff --git a/bootutil/src/image_validate.c b/bootutil/src/image_validate.c
new file mode 100644
index 0000000..98fdc9b
--- /dev/null
+++ b/bootutil/src/image_validate.c
@@ -0,0 +1,200 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#include <assert.h>
+#include <stddef.h>
+#include <inttypes.h>
+#include <string.h>
+
+#include "syscfg/syscfg.h"
+#include "hal/hal_flash.h"
+#include "flash_map/flash_map.h"
+#include "bootutil/image.h"
+#include "bootutil/sign_key.h"
+
+#include "mbedtls/sha256.h"
+#include "mbedtls/rsa.h"
+#include "mbedtls/ecdsa.h"
+#include "mbedtls/asn1.h"
+
+#include "bootutil_priv.h"
+
+/*
+ * Compute SHA256 over the image.
+ */
+static int
+bootutil_img_hash(struct image_header *hdr, const struct flash_area *fap,
+                  uint8_t *tmp_buf, uint32_t tmp_buf_sz,
+                  uint8_t *hash_result, uint8_t *seed, int seed_len)
+{
+    mbedtls_sha256_context sha256_ctx;
+    uint32_t blk_sz;
+    uint32_t size;
+    uint32_t off;
+    int rc;
+
+    mbedtls_sha256_init(&sha256_ctx);
+    mbedtls_sha256_starts(&sha256_ctx, 0);
+
+    /* in some cases (split image) the hash is seeded with data from
+     * the loader image */
+    if(seed && (seed_len > 0)) {
+        mbedtls_sha256_update(&sha256_ctx, seed, seed_len);
+    }
+
+    size = hdr->ih_img_size + hdr->ih_hdr_size;
+
+    /*
+     * Hash is computed over image header and image itself. No TLV is
+     * included ATM.
+     */
+    size = hdr->ih_img_size + hdr->ih_hdr_size;
+    for (off = 0; off < size; off += blk_sz) {
+        blk_sz = size - off;
+        if (blk_sz > tmp_buf_sz) {
+            blk_sz = tmp_buf_sz;
+        }
+        rc = flash_area_read(fap, off, tmp_buf, blk_sz);
+        if (rc) {
+            return rc;
+        }
+        mbedtls_sha256_update(&sha256_ctx, tmp_buf, blk_sz);
+    }
+    mbedtls_sha256_finish(&sha256_ctx, hash_result);
+
+    return 0;
+}
+
+/*
+ * Verify the integrity of the image.
+ * Return non-zero if image could not be validated/does not validate.
+ */
+int
+bootutil_img_validate(struct image_header *hdr, const struct flash_area *fap,
+                      uint8_t *tmp_buf, uint32_t tmp_buf_sz,
+                      uint8_t *seed, int seed_len, uint8_t *out_hash)
+{
+    uint32_t off;
+    uint32_t size;
+    uint32_t sha_off = 0;
+#if MYNEWT_VAL(BOOTUTIL_SIGN_RSA) || MYNEWT_VAL(BOOTUTIL_SIGN_EC)
+    uint32_t sig_off = 0;
+    uint32_t sig_len = 0;
+#endif
+    struct image_tlv tlv;
+    uint8_t buf[256];
+    uint8_t hash[32];
+    int rc;
+
+#if MYNEWT_VAL(BOOTUTIL_SIGN_RSA)
+    if ((hdr->ih_flags & IMAGE_F_PKCS15_RSA2048_SHA256) == 0) {
+        return -1;
+    }
+#endif
+#if MYNEWT_VAL(BOOTUTIL_SIGN_EC)
+    if ((hdr->ih_flags & IMAGE_F_ECDSA224_SHA256) == 0) {
+        return -1;
+    }
+#endif
+    if ((hdr->ih_flags & IMAGE_F_SHA256) == 0) {
+        return -1;
+    }
+
+    rc = bootutil_img_hash(hdr, fap, tmp_buf, tmp_buf_sz, hash,
+                           seed, seed_len);
+    if (rc) {
+        return rc;
+    }
+
+    if (out_hash) {
+        memcpy(out_hash, hash, 32);
+    }
+
+    /* After image there are TLVs. */
+    off = hdr->ih_img_size + hdr->ih_hdr_size;
+    size = off + hdr->ih_tlv_size;
+
+    for (; off < size; off += sizeof(tlv) + tlv.it_len) {
+        rc = flash_area_read(fap, off, &tlv, sizeof tlv);
+        if (rc) {
+            return rc;
+        }
+        if (tlv.it_type == IMAGE_TLV_SHA256) {
+            if (tlv.it_len != sizeof(hash)) {
+                return -1;
+            }
+            sha_off = off + sizeof(tlv);
+        }
+#if MYNEWT_VAL(BOOTUTIL_SIGN_RSA)
+        if (tlv.it_type == IMAGE_TLV_RSA2048) {
+            if (tlv.it_len != 256) { /* 2048 bits */
+                return -1;
+            }
+            sig_off = off + sizeof(tlv);
+            sig_len = tlv.it_len;
+        }
+#endif
+#if MYNEWT_VAL(BOOTUTIL_SIGN_EC)
+        if (tlv.it_type == IMAGE_TLV_ECDSA224) {
+            if (tlv.it_len < 64) { /* oids + 2 * 28 bytes */
+                return -1;
+            }
+            sig_off = off + sizeof(tlv);
+            sig_len = tlv.it_len;
+        }
+#endif
+    }
+    if (hdr->ih_flags & IMAGE_F_SHA256) {
+        if (!sha_off) {
+            /*
+             * Header said there should be hash TLV, no TLV found.
+             */
+            return -1;
+        }
+        rc = flash_area_read(fap, sha_off, buf, sizeof hash);
+        if (rc) {
+            return rc;
+        }
+        if (memcmp(hash, buf, sizeof(hash))) {
+            return -1;
+        }
+    }
+#if MYNEWT_VAL(BOOTUTIL_SIGN_RSA) || MYNEWT_VAL(BOOTUTIL_SIGN_EC)
+    if (!sig_off) {
+        /*
+         * Header said there should be PKCS1.v5 signature, no TLV
+         * found.
+         */
+        return -1;
+    }
+    rc = flash_area_read(fap, sig_off, buf, sig_len);
+    if (rc) {
+        return -1;
+    }
+
+    if (hdr->ih_key_id >= bootutil_key_cnt) {
+        return -1;
+    }
+    rc = bootutil_verify_sig(hash, sizeof(hash), buf, sig_len, hdr->ih_key_id);
+    if (rc) {
+        return -1;
+    }
+#endif
+    return 0;
+}