diff --git a/verifier28/asn1_decoder.cpp b/verifier28/asn1_decoder.cpp
new file mode 100644
index 0000000..285214f
--- /dev/null
+++ b/verifier28/asn1_decoder.cpp
@@ -0,0 +1,158 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed 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 "asn1_decoder.h"
+
+#include <stdint.h>
+
+int asn1_context::peek_byte() const {
+  if (length_ == 0) {
+    return -1;
+  }
+  return *p_;
+}
+
+int asn1_context::get_byte() {
+  if (length_ == 0) {
+    return -1;
+  }
+
+  int byte = *p_;
+  p_++;
+  length_--;
+  return byte;
+}
+
+bool asn1_context::skip_bytes(size_t num_skip) {
+  if (length_ < num_skip) {
+    return false;
+  }
+  p_ += num_skip;
+  length_ -= num_skip;
+  return true;
+}
+
+bool asn1_context::decode_length(size_t* out_len) {
+  int num_octets = get_byte();
+  if (num_octets == -1) {
+    return false;
+  }
+  if ((num_octets & 0x80) == 0x00) {
+    *out_len = num_octets;
+    return true;
+  }
+  num_octets &= kMaskTag;
+  if (static_cast<size_t>(num_octets) >= sizeof(size_t)) {
+    return false;
+  }
+  size_t length = 0;
+  for (int i = 0; i < num_octets; ++i) {
+    int byte = get_byte();
+    if (byte == -1) {
+      return false;
+    }
+    length <<= 8;
+    length += byte;
+  }
+  *out_len = length;
+  return true;
+}
+
+/**
+ * Returns the constructed type and advances the pointer. E.g. A0 -> 0
+ */
+asn1_context* asn1_context::asn1_constructed_get() {
+  int type = get_byte();
+  if (type == -1 || (type & kMaskConstructed) != kTagConstructed) {
+    return nullptr;
+  }
+  size_t length;
+  if (!decode_length(&length) || length > length_) {
+    return nullptr;
+  }
+  asn1_context* app_ctx = new asn1_context(p_, length);
+  app_ctx->app_type_ = type & kMaskAppType;
+  return app_ctx;
+}
+
+bool asn1_context::asn1_constructed_skip_all() {
+  int byte = peek_byte();
+  while (byte != -1 && (byte & kMaskConstructed) == kTagConstructed) {
+    skip_bytes(1);
+    size_t length;
+    if (!decode_length(&length) || !skip_bytes(length)) {
+      return false;
+    }
+    byte = peek_byte();
+  }
+  return byte != -1;
+}
+
+int asn1_context::asn1_constructed_type() const {
+  return app_type_;
+}
+
+asn1_context* asn1_context::asn1_sequence_get() {
+  if ((get_byte() & kMaskTag) != kTagSequence) {
+    return nullptr;
+  }
+  size_t length;
+  if (!decode_length(&length) || length > length_) {
+    return nullptr;
+  }
+  return new asn1_context(p_, length);
+}
+
+asn1_context* asn1_context::asn1_set_get() {
+  if ((get_byte() & kMaskTag) != kTagSet) {
+    return nullptr;
+  }
+  size_t length;
+  if (!decode_length(&length) || length > length_) {
+    return nullptr;
+  }
+  return new asn1_context(p_, length);
+}
+
+bool asn1_context::asn1_sequence_next() {
+  size_t length;
+  if (get_byte() == -1 || !decode_length(&length) || !skip_bytes(length)) {
+    return false;
+  }
+  return true;
+}
+
+bool asn1_context::asn1_oid_get(const uint8_t** oid, size_t* length) {
+  if (get_byte() != kTagOid) {
+    return false;
+  }
+  if (!decode_length(length) || *length == 0 || *length > length_) {
+    return false;
+  }
+  *oid = p_;
+  return true;
+}
+
+bool asn1_context::asn1_octet_string_get(const uint8_t** octet_string, size_t* length) {
+  if (get_byte() != kTagOctetString) {
+    return false;
+  }
+  if (!decode_length(length) || *length == 0 || *length > length_) {
+    return false;
+  }
+  *octet_string = p_;
+  return true;
+}
diff --git a/verifier28/asn1_decoder.h b/verifier28/asn1_decoder.h
new file mode 100644
index 0000000..3e99211
--- /dev/null
+++ b/verifier28/asn1_decoder.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed 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.
+ */
+
+#ifndef ASN1_DECODER_H_
+#define ASN1_DECODER_H_
+
+#include <stdint.h>
+
+class asn1_context {
+ public:
+  asn1_context(const uint8_t* buffer, size_t length) : p_(buffer), length_(length), app_type_(0) {}
+  int asn1_constructed_type() const;
+  asn1_context* asn1_constructed_get();
+  bool asn1_constructed_skip_all();
+  asn1_context* asn1_sequence_get();
+  asn1_context* asn1_set_get();
+  bool asn1_sequence_next();
+  bool asn1_oid_get(const uint8_t** oid, size_t* length);
+  bool asn1_octet_string_get(const uint8_t** octet_string, size_t* length);
+
+ private:
+  static constexpr int kMaskConstructed = 0xE0;
+  static constexpr int kMaskTag = 0x7F;
+  static constexpr int kMaskAppType = 0x1F;
+
+  static constexpr int kTagOctetString = 0x04;
+  static constexpr int kTagOid = 0x06;
+  static constexpr int kTagSequence = 0x30;
+  static constexpr int kTagSet = 0x31;
+  static constexpr int kTagConstructed = 0xA0;
+
+  int peek_byte() const;
+  int get_byte();
+  bool skip_bytes(size_t num_skip);
+  bool decode_length(size_t* out_len);
+
+  const uint8_t* p_;
+  size_t length_;
+  int app_type_;
+};
+
+#endif /* ASN1_DECODER_H_ */
diff --git a/verifier28/verifier.cpp b/verifier28/verifier.cpp
new file mode 100644
index 0000000..283e043
--- /dev/null
+++ b/verifier28/verifier.cpp
@@ -0,0 +1,553 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ *
+ * Licensed 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 "verifier.h"
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <algorithm>
+#include <functional>
+#include <memory>
+#include <vector>
+
+#include <android-base/logging.h>
+#include <openssl/bn.h>
+#include <openssl/ecdsa.h>
+#include <openssl/obj_mac.h>
+
+#include "asn1_decoder.h"
+#include "otautil/print_sha1.h"
+
+static constexpr size_t MiB = 1024 * 1024;
+
+/*
+ * Simple version of PKCS#7 SignedData extraction. This extracts the
+ * signature OCTET STRING to be used for signature verification.
+ *
+ * For full details, see http://www.ietf.org/rfc/rfc3852.txt
+ *
+ * The PKCS#7 structure looks like:
+ *
+ *   SEQUENCE (ContentInfo)
+ *     OID (ContentType)
+ *     [0] (content)
+ *       SEQUENCE (SignedData)
+ *         INTEGER (version CMSVersion)
+ *         SET (DigestAlgorithmIdentifiers)
+ *         SEQUENCE (EncapsulatedContentInfo)
+ *         [0] (CertificateSet OPTIONAL)
+ *         [1] (RevocationInfoChoices OPTIONAL)
+ *         SET (SignerInfos)
+ *           SEQUENCE (SignerInfo)
+ *             INTEGER (CMSVersion)
+ *             SEQUENCE (SignerIdentifier)
+ *             SEQUENCE (DigestAlgorithmIdentifier)
+ *             SEQUENCE (SignatureAlgorithmIdentifier)
+ *             OCTET STRING (SignatureValue)
+ */
+static bool read_pkcs7(const uint8_t* pkcs7_der, size_t pkcs7_der_len,
+                       std::vector<uint8_t>* sig_der) {
+  CHECK(sig_der != nullptr);
+  sig_der->clear();
+
+  asn1_context ctx(pkcs7_der, pkcs7_der_len);
+
+  std::unique_ptr<asn1_context> pkcs7_seq(ctx.asn1_sequence_get());
+  if (pkcs7_seq == nullptr || !pkcs7_seq->asn1_sequence_next()) {
+    return false;
+  }
+
+  std::unique_ptr<asn1_context> signed_data_app(pkcs7_seq->asn1_constructed_get());
+  if (signed_data_app == nullptr) {
+    return false;
+  }
+
+  std::unique_ptr<asn1_context> signed_data_seq(signed_data_app->asn1_sequence_get());
+  if (signed_data_seq == nullptr ||
+      !signed_data_seq->asn1_sequence_next() ||
+      !signed_data_seq->asn1_sequence_next() ||
+      !signed_data_seq->asn1_sequence_next() ||
+      !signed_data_seq->asn1_constructed_skip_all()) {
+    return false;
+  }
+
+  std::unique_ptr<asn1_context> sig_set(signed_data_seq->asn1_set_get());
+  if (sig_set == nullptr) {
+    return false;
+  }
+
+  std::unique_ptr<asn1_context> sig_seq(sig_set->asn1_sequence_get());
+  if (sig_seq == nullptr ||
+      !sig_seq->asn1_sequence_next() ||
+      !sig_seq->asn1_sequence_next() ||
+      !sig_seq->asn1_sequence_next() ||
+      !sig_seq->asn1_sequence_next()) {
+    return false;
+  }
+
+  const uint8_t* sig_der_ptr;
+  size_t sig_der_length;
+  if (!sig_seq->asn1_octet_string_get(&sig_der_ptr, &sig_der_length)) {
+    return false;
+  }
+
+  sig_der->resize(sig_der_length);
+  std::copy(sig_der_ptr, sig_der_ptr + sig_der_length, sig_der->begin());
+  return true;
+}
+
+/*
+ * Looks for an RSA signature embedded in the .ZIP file comment given the path to the zip. Verifies
+ * that it matches one of the given public keys. A callback function can be optionally provided for
+ * posting the progress.
+ *
+ * Returns VERIFY_SUCCESS or VERIFY_FAILURE (if any error is encountered or no key matches the
+ * signature).
+ */
+int verify_file(const unsigned char* addr, size_t length, const std::vector<Certificate>& keys,
+                const std::function<void(float)>& set_progress) {
+  if (set_progress) {
+    set_progress(0.0);
+  }
+
+  // An archive with a whole-file signature will end in six bytes:
+  //
+  //   (2-byte signature start) $ff $ff (2-byte comment size)
+  //
+  // (As far as the ZIP format is concerned, these are part of the archive comment.) We start by
+  // reading this footer, this tells us how far back from the end we have to start reading to find
+  // the whole comment.
+
+#define FOOTER_SIZE 6
+
+  if (length < FOOTER_SIZE) {
+    LOG(ERROR) << "not big enough to contain footer";
+    return VERIFY_FAILURE;
+  }
+
+  const unsigned char* footer = addr + length - FOOTER_SIZE;
+
+  if (footer[2] != 0xff || footer[3] != 0xff) {
+    LOG(ERROR) << "footer is wrong";
+    return VERIFY_FAILURE;
+  }
+
+  size_t comment_size = footer[4] + (footer[5] << 8);
+  size_t signature_start = footer[0] + (footer[1] << 8);
+  LOG(INFO) << "comment is " << comment_size << " bytes; signature is " << signature_start
+            << " bytes from end";
+
+  if (signature_start > comment_size) {
+    LOG(ERROR) << "signature start: " << signature_start << " is larger than comment size: "
+               << comment_size;
+    return VERIFY_FAILURE;
+  }
+
+  if (signature_start <= FOOTER_SIZE) {
+    LOG(ERROR) << "Signature start is in the footer";
+    return VERIFY_FAILURE;
+  }
+
+#define EOCD_HEADER_SIZE 22
+
+  // The end-of-central-directory record is 22 bytes plus any comment length.
+  size_t eocd_size = comment_size + EOCD_HEADER_SIZE;
+
+  if (length < eocd_size) {
+    LOG(ERROR) << "not big enough to contain EOCD";
+    return VERIFY_FAILURE;
+  }
+
+  // Determine how much of the file is covered by the signature. This is everything except the
+  // signature data and length, which includes all of the EOCD except for the comment length field
+  // (2 bytes) and the comment data.
+  size_t signed_len = length - eocd_size + EOCD_HEADER_SIZE - 2;
+
+  const unsigned char* eocd = addr + length - eocd_size;
+
+  // If this is really is the EOCD record, it will begin with the magic number $50 $4b $05 $06.
+  if (eocd[0] != 0x50 || eocd[1] != 0x4b || eocd[2] != 0x05 || eocd[3] != 0x06) {
+    LOG(ERROR) << "signature length doesn't match EOCD marker";
+    return VERIFY_FAILURE;
+  }
+
+  for (size_t i = 4; i < eocd_size-3; ++i) {
+    if (eocd[i] == 0x50 && eocd[i+1] == 0x4b && eocd[i+2] == 0x05 && eocd[i+3] == 0x06) {
+      // If the sequence $50 $4b $05 $06 appears anywhere after the real one, libziparchive will
+      // find the later (wrong) one, which could be exploitable. Fail the verification if this
+      // sequence occurs anywhere after the real one.
+      LOG(ERROR) << "EOCD marker occurs after start of EOCD";
+      return VERIFY_FAILURE;
+    }
+  }
+
+  bool need_sha1 = false;
+  bool need_sha256 = false;
+  for (const auto& key : keys) {
+    switch (key.hash_len) {
+      case SHA_DIGEST_LENGTH: need_sha1 = true; break;
+      case SHA256_DIGEST_LENGTH: need_sha256 = true; break;
+    }
+  }
+
+  SHA_CTX sha1_ctx;
+  SHA256_CTX sha256_ctx;
+  SHA1_Init(&sha1_ctx);
+  SHA256_Init(&sha256_ctx);
+
+  double frac = -1.0;
+  size_t so_far = 0;
+  while (so_far < signed_len) {
+    // On a Nexus 5X, experiment showed 16MiB beat 1MiB by 6% faster for a
+    // 1196MiB full OTA and 60% for an 89MiB incremental OTA.
+    // http://b/28135231.
+    size_t size = std::min(signed_len - so_far, 16 * MiB);
+
+    if (need_sha1) SHA1_Update(&sha1_ctx, addr + so_far, size);
+    if (need_sha256) SHA256_Update(&sha256_ctx, addr + so_far, size);
+    so_far += size;
+
+    if (set_progress) {
+      double f = so_far / (double)signed_len;
+      if (f > frac + 0.02 || size == so_far) {
+        set_progress(f);
+        frac = f;
+      }
+    }
+  }
+
+  uint8_t sha1[SHA_DIGEST_LENGTH];
+  SHA1_Final(sha1, &sha1_ctx);
+  uint8_t sha256[SHA256_DIGEST_LENGTH];
+  SHA256_Final(sha256, &sha256_ctx);
+
+  const uint8_t* signature = eocd + eocd_size - signature_start;
+  size_t signature_size = signature_start - FOOTER_SIZE;
+
+  LOG(INFO) << "signature (offset: " << std::hex << (length - signature_start) << ", length: "
+            << signature_size << "): " << print_hex(signature, signature_size);
+
+  std::vector<uint8_t> sig_der;
+  if (!read_pkcs7(signature, signature_size, &sig_der)) {
+    LOG(ERROR) << "Could not find signature DER block";
+    return VERIFY_FAILURE;
+  }
+
+  // Check to make sure at least one of the keys matches the signature. Since any key can match,
+  // we need to try each before determining a verification failure has happened.
+  size_t i = 0;
+  for (const auto& key : keys) {
+    const uint8_t* hash;
+    int hash_nid;
+    switch (key.hash_len) {
+      case SHA_DIGEST_LENGTH:
+        hash = sha1;
+        hash_nid = NID_sha1;
+        break;
+      case SHA256_DIGEST_LENGTH:
+        hash = sha256;
+        hash_nid = NID_sha256;
+        break;
+      default:
+        continue;
+    }
+
+    // The 6 bytes is the "(signature_start) $ff $ff (comment_size)" that the signing tool appends
+    // after the signature itself.
+    if (key.key_type == Certificate::KEY_TYPE_RSA) {
+      if (!RSA_verify(hash_nid, hash, key.hash_len, sig_der.data(), sig_der.size(),
+                      key.rsa.get())) {
+        LOG(INFO) << "failed to verify against RSA key " << i;
+        continue;
+      }
+
+      LOG(INFO) << "whole-file signature verified against RSA key " << i;
+      return VERIFY_SUCCESS;
+    } else if (key.key_type == Certificate::KEY_TYPE_EC && key.hash_len == SHA256_DIGEST_LENGTH) {
+      if (!ECDSA_verify(0, hash, key.hash_len, sig_der.data(), sig_der.size(), key.ec.get())) {
+        LOG(INFO) << "failed to verify against EC key " << i;
+        continue;
+      }
+
+      LOG(INFO) << "whole-file signature verified against EC key " << i;
+      return VERIFY_SUCCESS;
+    } else {
+      LOG(INFO) << "Unknown key type " << key.key_type;
+    }
+    i++;
+  }
+
+  if (need_sha1) {
+    LOG(INFO) << "SHA-1 digest: " << print_hex(sha1, SHA_DIGEST_LENGTH);
+  }
+  if (need_sha256) {
+    LOG(INFO) << "SHA-256 digest: " << print_hex(sha256, SHA256_DIGEST_LENGTH);
+  }
+  LOG(ERROR) << "failed to verify whole-file signature";
+  return VERIFY_FAILURE;
+}
+
+std::unique_ptr<RSA, RSADeleter> parse_rsa_key(FILE* file, uint32_t exponent) {
+    // Read key length in words and n0inv. n0inv is a precomputed montgomery
+    // parameter derived from the modulus and can be used to speed up
+    // verification. n0inv is 32 bits wide here, assuming the verification logic
+    // uses 32 bit arithmetic. However, BoringSSL may use a word size of 64 bits
+    // internally, in which case we don't have a valid n0inv. Thus, we just
+    // ignore the montgomery parameters and have BoringSSL recompute them
+    // internally. If/When the speedup from using the montgomery parameters
+    // becomes relevant, we can add more sophisticated code here to obtain a
+    // 64-bit n0inv and initialize the montgomery parameters in the key object.
+    uint32_t key_len_words = 0;
+    uint32_t n0inv = 0;
+    if (fscanf(file, " %i , 0x%x", &key_len_words, &n0inv) != 2) {
+        return nullptr;
+    }
+
+    if (key_len_words > 8192 / 32) {
+        LOG(ERROR) << "key length (" << key_len_words << ") too large";
+        return nullptr;
+    }
+
+    // Read the modulus.
+    std::unique_ptr<uint32_t[]> modulus(new uint32_t[key_len_words]);
+    if (fscanf(file, " , { %u", &modulus[0]) != 1) {
+        return nullptr;
+    }
+    for (uint32_t i = 1; i < key_len_words; ++i) {
+        if (fscanf(file, " , %u", &modulus[i]) != 1) {
+            return nullptr;
+        }
+    }
+
+    // Cconvert from little-endian array of little-endian words to big-endian
+    // byte array suitable as input for BN_bin2bn.
+    std::reverse((uint8_t*)modulus.get(),
+                 (uint8_t*)(modulus.get() + key_len_words));
+
+    // The next sequence of values is the montgomery parameter R^2. Since we
+    // generally don't have a valid |n0inv|, we ignore this (see comment above).
+    uint32_t rr_value;
+    if (fscanf(file, " } , { %u", &rr_value) != 1) {
+        return nullptr;
+    }
+    for (uint32_t i = 1; i < key_len_words; ++i) {
+        if (fscanf(file, " , %u", &rr_value) != 1) {
+            return nullptr;
+        }
+    }
+    if (fscanf(file, " } } ") != 0) {
+        return nullptr;
+    }
+
+    // Initialize the key.
+    std::unique_ptr<RSA, RSADeleter> key(RSA_new());
+    if (!key) {
+      return nullptr;
+    }
+
+    key->n = BN_bin2bn((uint8_t*)modulus.get(),
+                       key_len_words * sizeof(uint32_t), NULL);
+    if (!key->n) {
+      return nullptr;
+    }
+
+    key->e = BN_new();
+    if (!key->e || !BN_set_word(key->e, exponent)) {
+      return nullptr;
+    }
+
+    return key;
+}
+
+struct BNDeleter {
+  void operator()(BIGNUM* bn) const {
+    BN_free(bn);
+  }
+};
+
+std::unique_ptr<EC_KEY, ECKEYDeleter> parse_ec_key(FILE* file) {
+    uint32_t key_len_bytes = 0;
+    if (fscanf(file, " %i", &key_len_bytes) != 1) {
+        return nullptr;
+    }
+
+    std::unique_ptr<EC_GROUP, void (*)(EC_GROUP*)> group(
+        EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1), EC_GROUP_free);
+    if (!group) {
+        return nullptr;
+    }
+
+    // Verify that |key_len| matches the group order.
+    if (key_len_bytes != BN_num_bytes(EC_GROUP_get0_order(group.get()))) {
+        return nullptr;
+    }
+
+    // Read the public key coordinates. Note that the byte order in the file is
+    // little-endian, so we convert to big-endian here.
+    std::unique_ptr<uint8_t[]> bytes(new uint8_t[key_len_bytes]);
+    std::unique_ptr<BIGNUM, BNDeleter> point[2];
+    for (int i = 0; i < 2; ++i) {
+        unsigned int byte = 0;
+        if (fscanf(file, " , { %u", &byte) != 1) {
+            return nullptr;
+        }
+        bytes[key_len_bytes - 1] = byte;
+
+        for (size_t i = 1; i < key_len_bytes; ++i) {
+            if (fscanf(file, " , %u", &byte) != 1) {
+                return nullptr;
+            }
+            bytes[key_len_bytes - i - 1] = byte;
+        }
+
+        point[i].reset(BN_bin2bn(bytes.get(), key_len_bytes, nullptr));
+        if (!point[i]) {
+            return nullptr;
+        }
+
+        if (fscanf(file, " }") != 0) {
+            return nullptr;
+        }
+    }
+
+    if (fscanf(file, " } ") != 0) {
+        return nullptr;
+    }
+
+    // Create and initialize the key.
+    std::unique_ptr<EC_KEY, ECKEYDeleter> key(EC_KEY_new());
+    if (!key || !EC_KEY_set_group(key.get(), group.get()) ||
+        !EC_KEY_set_public_key_affine_coordinates(key.get(), point[0].get(),
+                                                  point[1].get())) {
+        return nullptr;
+    }
+
+    return key;
+}
+
+// Reads a file containing one or more public keys as produced by
+// DumpPublicKey:  this is an RSAPublicKey struct as it would appear
+// as a C source literal, eg:
+//
+//  "{64,0xc926ad21,{1795090719,...,-695002876},{-857949815,...,1175080310}}"
+//
+// For key versions newer than the original 2048-bit e=3 keys
+// supported by Android, the string is preceded by a version
+// identifier, eg:
+//
+//  "v2 {64,0xc926ad21,{1795090719,...,-695002876},{-857949815,...,1175080310}}"
+//
+// (Note that the braces and commas in this example are actual
+// characters the parser expects to find in the file; the ellipses
+// indicate more numbers omitted from this example.)
+//
+// The file may contain multiple keys in this format, separated by
+// commas.  The last key must not be followed by a comma.
+//
+// A Certificate is a pair of an RSAPublicKey and a particular hash
+// (we support SHA-1 and SHA-256; we store the hash length to signify
+// which is being used).  The hash used is implied by the version number.
+//
+//       1: 2048-bit RSA key with e=3 and SHA-1 hash
+//       2: 2048-bit RSA key with e=65537 and SHA-1 hash
+//       3: 2048-bit RSA key with e=3 and SHA-256 hash
+//       4: 2048-bit RSA key with e=65537 and SHA-256 hash
+//       5: 256-bit EC key using the NIST P-256 curve parameters and SHA-256 hash
+//
+// Returns true on success, and appends the found keys (at least one) to certs.
+// Otherwise returns false if the file failed to parse, or if it contains zero
+// keys. The contents in certs would be unspecified on failure.
+bool load_keys(const char* filename, std::vector<Certificate>& certs) {
+  std::unique_ptr<FILE, decltype(&fclose)> f(fopen(filename, "re"), fclose);
+  if (!f) {
+    PLOG(ERROR) << "error opening " << filename;
+    return false;
+  }
+
+  while (true) {
+    certs.emplace_back(0, Certificate::KEY_TYPE_RSA, nullptr, nullptr);
+    Certificate& cert = certs.back();
+    uint32_t exponent = 0;
+
+    char start_char;
+    if (fscanf(f.get(), " %c", &start_char) != 1) return false;
+    if (start_char == '{') {
+      // a version 1 key has no version specifier.
+      cert.key_type = Certificate::KEY_TYPE_RSA;
+      exponent = 3;
+      cert.hash_len = SHA_DIGEST_LENGTH;
+    } else if (start_char == 'v') {
+      int version;
+      if (fscanf(f.get(), "%d {", &version) != 1) return false;
+      switch (version) {
+        case 2:
+          cert.key_type = Certificate::KEY_TYPE_RSA;
+          exponent = 65537;
+          cert.hash_len = SHA_DIGEST_LENGTH;
+          break;
+        case 3:
+          cert.key_type = Certificate::KEY_TYPE_RSA;
+          exponent = 3;
+          cert.hash_len = SHA256_DIGEST_LENGTH;
+          break;
+        case 4:
+          cert.key_type = Certificate::KEY_TYPE_RSA;
+          exponent = 65537;
+          cert.hash_len = SHA256_DIGEST_LENGTH;
+          break;
+        case 5:
+          cert.key_type = Certificate::KEY_TYPE_EC;
+          cert.hash_len = SHA256_DIGEST_LENGTH;
+          break;
+        default:
+          return false;
+      }
+    }
+
+    if (cert.key_type == Certificate::KEY_TYPE_RSA) {
+      cert.rsa = parse_rsa_key(f.get(), exponent);
+      if (!cert.rsa) {
+        return false;
+      }
+
+      LOG(INFO) << "read key e=" << exponent << " hash=" << cert.hash_len;
+    } else if (cert.key_type == Certificate::KEY_TYPE_EC) {
+      cert.ec = parse_ec_key(f.get());
+      if (!cert.ec) {
+        return false;
+      }
+    } else {
+      LOG(ERROR) << "Unknown key type " << cert.key_type;
+      return false;
+    }
+
+    // if the line ends in a comma, this file has more keys.
+    int ch = fgetc(f.get());
+    if (ch == ',') {
+      // more keys to come.
+      continue;
+    } else if (ch == EOF) {
+      break;
+    } else {
+      LOG(ERROR) << "unexpected character between keys";
+      return false;
+    }
+  }
+  return true;
+}
diff --git a/verifier28/verifier.h b/verifier28/verifier.h
new file mode 100644
index 0000000..665e5a9
--- /dev/null
+++ b/verifier28/verifier.h
@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ *
+ * Licensed 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.
+ */
+
+#ifndef _RECOVERY_VERIFIER_H
+#define _RECOVERY_VERIFIER_H
+
+#include <functional>
+#include <memory>
+#include <vector>
+
+#include <openssl/ec_key.h>
+#include <openssl/rsa.h>
+#include <openssl/sha.h>
+
+#define ASSUMED_UPDATE_BINARY_NAME  "META-INF/com/google/android/update-binary"
+
+enum { INSTALL_SUCCESS, INSTALL_ERROR, INSTALL_CORRUPT, INSTALL_RETRY };
+
+static const float VERIFICATION_PROGRESS_FRAC = 0.25;
+
+struct RSADeleter {
+  void operator()(RSA* rsa) const {
+    RSA_free(rsa);
+  }
+};
+
+struct ECKEYDeleter {
+  void operator()(EC_KEY* ec_key) const {
+    EC_KEY_free(ec_key);
+  }
+};
+
+struct Certificate {
+    typedef enum {
+        KEY_TYPE_RSA,
+        KEY_TYPE_EC,
+    } KeyType;
+
+    Certificate(int hash_len_,
+                KeyType key_type_,
+                std::unique_ptr<RSA, RSADeleter>&& rsa_,
+                std::unique_ptr<EC_KEY, ECKEYDeleter>&& ec_)
+        : hash_len(hash_len_),
+          key_type(key_type_),
+          rsa(std::move(rsa_)),
+          ec(std::move(ec_)) {}
+
+    // SHA_DIGEST_LENGTH (SHA-1) or SHA256_DIGEST_LENGTH (SHA-256)
+    int hash_len;
+    KeyType key_type;
+    std::unique_ptr<RSA, RSADeleter> rsa;
+    std::unique_ptr<EC_KEY, ECKEYDeleter> ec;
+};
+
+/*
+ * 'addr' and 'length' define an update package file that has been loaded (or mmap'ed, or
+ * whatever) into memory. Verifies that the file is signed and the signature matches one of the
+ * given keys. It optionally accepts a callback function for posting the progress to. Returns one
+ * of the constants of VERIFY_SUCCESS and VERIFY_FAILURE.
+ */
+int verify_file(const unsigned char* addr, size_t length, const std::vector<Certificate>& keys,
+                const std::function<void(float)>& set_progress = nullptr);
+
+bool load_keys(const char* filename, std::vector<Certificate>& certs);
+
+#define VERIFY_SUCCESS        0
+#define VERIFY_FAILURE        1
+
+#endif  /* _RECOVERY_VERIFIER_H */