diff --git a/security/keymint/aidl/vts/functional/AttestKeyTest.cpp b/security/keymint/aidl/vts/functional/AttestKeyTest.cpp
index daa3e18..4e951d6 100644
--- a/security/keymint/aidl/vts/functional/AttestKeyTest.cpp
+++ b/security/keymint/aidl/vts/functional/AttestKeyTest.cpp
@@ -35,6 +35,12 @@
 
 using AttestKeyTest = KeyMintAidlTestBase;
 
+/*
+ * AttestKeyTest.AllRsaSizes
+ *
+ * This test creates self signed RSA attestation keys of various sizes, and verify they can be
+ * used to sign other RSA and EC keys.
+ */
 TEST_P(AttestKeyTest, AllRsaSizes) {
     for (auto size : ValidKeySizes(Algorithm::RSA)) {
         /*
@@ -54,7 +60,7 @@
         EXPECT_TRUE(IsSelfSigned(attest_key_cert_chain)) << "Failed on size " << size;
 
         /*
-         * Use attestation key to sign RSA key
+         * Use attestation key to sign RSA signing key
          */
         attest_key.issuerSubjectName = make_name_from_str("Android Keystore Key");
         vector<uint8_t> attested_key_blob;
@@ -81,14 +87,47 @@
         EXPECT_FALSE(ChainSignaturesAreValid(attested_key_cert_chain));
 
         // Appending the attest_key chain to the attested_key_chain should yield a valid chain.
-        if (attest_key_cert_chain.size() > 0) {
-            attested_key_cert_chain.push_back(attest_key_cert_chain[0]);
-        }
+        attested_key_cert_chain.push_back(attest_key_cert_chain[0]);
         EXPECT_TRUE(ChainSignaturesAreValid(attested_key_cert_chain));
+        EXPECT_EQ(attested_key_cert_chain.size(), 2);
+
+        /*
+         * Use attestation key to sign RSA decryption key
+         */
+        attested_key_characteristics.resize(0);
+        attested_key_cert_chain.resize(0);
+        EXPECT_EQ(ErrorCode::OK,
+                  GenerateKey(AuthorizationSetBuilder()
+                                      .RsaEncryptionKey(2048, 65537)
+                                      .Digest(Digest::NONE)
+                                      .Padding(PaddingMode::NONE)
+                                      .Authorization(TAG_NO_AUTH_REQUIRED)
+                                      .AttestationChallenge("foo2")
+                                      .AttestationApplicationId("bar2")
+                                      .SetDefaultValidity(),
+                              attest_key, &attested_key_blob, &attested_key_characteristics,
+                              &attested_key_cert_chain));
+
+        CheckedDeleteKey(&attested_key_blob);
+
+        hw_enforced = HwEnforcedAuthorizations(attested_key_characteristics);
+        sw_enforced = SwEnforcedAuthorizations(attested_key_characteristics);
+        EXPECT_TRUE(verify_attestation_record("foo2", "bar2", sw_enforced, hw_enforced, SecLevel(),
+                                              attested_key_cert_chain[0].encodedCertificate));
+
+        // Attestation by itself is not valid (last entry is not self-signed).
+        EXPECT_FALSE(ChainSignaturesAreValid(attested_key_cert_chain));
+
+        // Appending the attest_key chain to the attested_key_chain should yield a valid chain.
+        attested_key_cert_chain.push_back(attest_key_cert_chain[0]);
+        EXPECT_TRUE(ChainSignaturesAreValid(attested_key_cert_chain));
+        EXPECT_EQ(attested_key_cert_chain.size(), 2);
 
         /*
          * Use attestation key to sign EC key
          */
+        attested_key_characteristics.resize(0);
+        attested_key_cert_chain.resize(0);
         EXPECT_EQ(ErrorCode::OK,
                   GenerateKey(AuthorizationSetBuilder()
                                       .EcdsaSigningKey(EcCurve::P_256)
@@ -111,9 +150,7 @@
         EXPECT_FALSE(ChainSignaturesAreValid(attested_key_cert_chain));
 
         // Appending the attest_key chain to the attested_key_chain should yield a valid chain.
-        if (attest_key_cert_chain.size() > 0) {
-            attested_key_cert_chain.push_back(attest_key_cert_chain[0]);
-        }
+        attested_key_cert_chain.push_back(attest_key_cert_chain[0]);
         EXPECT_TRUE(ChainSignaturesAreValid(attested_key_cert_chain));
 
         // Bail early if anything failed.
@@ -121,6 +158,327 @@
     }
 }
 
+/*
+ * AttestKeyTest.RsaAttestedAttestKeys
+ *
+ * This test creates an RSA attestation key signed by factory keys, and varifies it can be
+ * used to sign other RSA and EC keys.
+ */
+TEST_P(AttestKeyTest, RsaAttestedAttestKeys) {
+    auto challenge = "hello";
+    auto app_id = "foo";
+
+    auto subject = "cert subj 2";
+    vector<uint8_t> subject_der(make_name_from_str(subject));
+
+    uint64_t serial_int = 66;
+    vector<uint8_t> serial_blob(build_serial_blob(serial_int));
+
+    /*
+     * Create attestation key.
+     */
+    AttestationKey attest_key;
+    vector<KeyCharacteristics> attest_key_characteristics;
+    vector<Certificate> attest_key_cert_chain;
+    ASSERT_EQ(ErrorCode::OK,
+              GenerateKey(AuthorizationSetBuilder()
+                                  .RsaSigningKey(2048, 65537)
+                                  .AttestKey()
+                                  .AttestationChallenge(challenge)
+                                  .AttestationApplicationId(app_id)
+                                  .Authorization(TAG_CERTIFICATE_SERIAL, serial_blob)
+                                  .Authorization(TAG_CERTIFICATE_SUBJECT, subject_der)
+                                  .Authorization(TAG_NO_AUTH_REQUIRED)
+                                  .SetDefaultValidity(),
+                          {} /* attestation signing key */, &attest_key.keyBlob,
+                          &attest_key_characteristics, &attest_key_cert_chain));
+
+    EXPECT_GT(attest_key_cert_chain.size(), 1);
+    verify_subject_and_serial(attest_key_cert_chain[0], serial_int, subject, false);
+    EXPECT_TRUE(ChainSignaturesAreValid(attest_key_cert_chain));
+
+    AuthorizationSet hw_enforced = HwEnforcedAuthorizations(attest_key_characteristics);
+    AuthorizationSet sw_enforced = SwEnforcedAuthorizations(attest_key_characteristics);
+    EXPECT_TRUE(verify_attestation_record(challenge, app_id,  //
+                                          sw_enforced, hw_enforced, SecLevel(),
+                                          attest_key_cert_chain[0].encodedCertificate));
+
+    /*
+     * Use attestation key to sign RSA key
+     */
+    attest_key.issuerSubjectName = subject_der;
+    vector<uint8_t> attested_key_blob;
+    vector<KeyCharacteristics> attested_key_characteristics;
+    vector<Certificate> attested_key_cert_chain;
+
+    auto subject2 = "cert subject";
+    vector<uint8_t> subject_der2(make_name_from_str(subject2));
+
+    uint64_t serial_int2 = 987;
+    vector<uint8_t> serial_blob2(build_serial_blob(serial_int2));
+
+    EXPECT_EQ(ErrorCode::OK,
+              GenerateKey(AuthorizationSetBuilder()
+                                  .RsaSigningKey(2048, 65537)
+                                  .Authorization(TAG_NO_AUTH_REQUIRED)
+                                  .AttestationChallenge("foo")
+                                  .AttestationApplicationId("bar")
+                                  .Authorization(TAG_CERTIFICATE_SERIAL, serial_blob2)
+                                  .Authorization(TAG_CERTIFICATE_SUBJECT, subject_der2)
+                                  .SetDefaultValidity(),
+                          attest_key, &attested_key_blob, &attested_key_characteristics,
+                          &attested_key_cert_chain));
+
+    CheckedDeleteKey(&attested_key_blob);
+    CheckedDeleteKey(&attest_key.keyBlob);
+
+    AuthorizationSet hw_enforced2 = HwEnforcedAuthorizations(attested_key_characteristics);
+    AuthorizationSet sw_enforced2 = SwEnforcedAuthorizations(attested_key_characteristics);
+    EXPECT_TRUE(verify_attestation_record("foo", "bar", sw_enforced2, hw_enforced2, SecLevel(),
+                                          attested_key_cert_chain[0].encodedCertificate));
+
+    // Attestation by itself is not valid (last entry is not self-signed).
+    EXPECT_FALSE(ChainSignaturesAreValid(attested_key_cert_chain));
+
+    // Appending the attest_key chain to the attested_key_chain should yield a valid chain.
+    attested_key_cert_chain.insert(attested_key_cert_chain.end(), attest_key_cert_chain.begin(),
+                                   attest_key_cert_chain.end());
+
+    EXPECT_TRUE(ChainSignaturesAreValid(attested_key_cert_chain));
+    EXPECT_GT(attested_key_cert_chain.size(), 2);
+    verify_subject_and_serial(attested_key_cert_chain[0], serial_int2, subject2, false);
+}
+
+/*
+ * AttestKeyTest.RsaAttestKeyChaining
+ *
+ * This test creates a chain of multiple RSA attest keys, each used to sign the next attest key,
+ * with the last attest key signed by the factory chain.
+ */
+TEST_P(AttestKeyTest, RsaAttestKeyChaining) {
+    const int chain_size = 6;
+    vector<vector<uint8_t>> key_blob_list(chain_size);
+    vector<vector<Certificate>> cert_chain_list(chain_size);
+
+    for (int i = 0; i < chain_size; i++) {
+        string sub = "attest key chaining ";
+        char index = '1' + i;
+        string subject = sub + index;
+        vector<uint8_t> subject_der(make_name_from_str(subject));
+
+        uint64_t serial_int = 7000 + i;
+        vector<uint8_t> serial_blob(build_serial_blob(serial_int));
+
+        vector<KeyCharacteristics> attested_key_characteristics;
+        AttestationKey attest_key;
+        optional<AttestationKey> attest_key_opt;
+
+        if (i > 0) {
+            attest_key.issuerSubjectName = make_name_from_str(sub + (char)(index - 1));
+            attest_key.keyBlob = key_blob_list[i - 1];
+            attest_key_opt = attest_key;
+        }
+
+        EXPECT_EQ(ErrorCode::OK,
+                  GenerateKey(AuthorizationSetBuilder()
+                                      .RsaSigningKey(2048, 65537)
+                                      .AttestKey()
+                                      .AttestationChallenge("foo")
+                                      .AttestationApplicationId("bar")
+                                      .Authorization(TAG_NO_AUTH_REQUIRED)
+                                      .Authorization(TAG_CERTIFICATE_SERIAL, serial_blob)
+                                      .Authorization(TAG_CERTIFICATE_SUBJECT, subject_der)
+                                      .SetDefaultValidity(),
+                              attest_key_opt, &key_blob_list[i], &attested_key_characteristics,
+                              &cert_chain_list[i]));
+
+        AuthorizationSet hw_enforced = HwEnforcedAuthorizations(attested_key_characteristics);
+        AuthorizationSet sw_enforced = SwEnforcedAuthorizations(attested_key_characteristics);
+        EXPECT_TRUE(verify_attestation_record("foo", "bar", sw_enforced, hw_enforced, SecLevel(),
+                                              cert_chain_list[i][0].encodedCertificate));
+
+        if (i > 0) {
+            /*
+             * The first key is attestated with factory chain, but all the rest of the keys are
+             * not supposed to be returned in attestation certificate chains.
+             */
+            EXPECT_FALSE(ChainSignaturesAreValid(cert_chain_list[i]));
+
+            // Appending the attest_key chain to the attested_key_chain should yield a valid chain.
+            cert_chain_list[i].insert(cert_chain_list[i].end(),        //
+                                      cert_chain_list[i - 1].begin(),  //
+                                      cert_chain_list[i - 1].end());
+        }
+
+        EXPECT_TRUE(ChainSignaturesAreValid(cert_chain_list[i]));
+        EXPECT_GT(cert_chain_list[i].size(), i + 1);
+        verify_subject_and_serial(cert_chain_list[i][0], serial_int, subject, false);
+    }
+
+    for (int i = 0; i < chain_size; i++) {
+        CheckedDeleteKey(&key_blob_list[i]);
+    }
+}
+
+/*
+ * AttestKeyTest.EcAttestKeyChaining
+ *
+ * This test creates a chain of multiple Ec attest keys, each used to sign the next attest key,
+ * with the last attest key signed by the factory chain.
+ */
+TEST_P(AttestKeyTest, EcAttestKeyChaining) {
+    const int chain_size = 6;
+    vector<vector<uint8_t>> key_blob_list(chain_size);
+    vector<vector<Certificate>> cert_chain_list(chain_size);
+
+    for (int i = 0; i < chain_size; i++) {
+        string sub = "Ec attest key chaining ";
+        char index = '1' + i;
+        string subject = sub + index;
+        vector<uint8_t> subject_der(make_name_from_str(subject));
+
+        uint64_t serial_int = 800000 + i;
+        vector<uint8_t> serial_blob(build_serial_blob(serial_int));
+
+        vector<KeyCharacteristics> attested_key_characteristics;
+        AttestationKey attest_key;
+        optional<AttestationKey> attest_key_opt;
+
+        if (i > 0) {
+            attest_key.issuerSubjectName = make_name_from_str(sub + (char)(index - 1));
+            attest_key.keyBlob = key_blob_list[i - 1];
+            attest_key_opt = attest_key;
+        }
+
+        EXPECT_EQ(ErrorCode::OK,
+                  GenerateKey(AuthorizationSetBuilder()
+                                      .EcdsaSigningKey(224)
+                                      .AttestKey()
+                                      .AttestationChallenge("foo")
+                                      .AttestationApplicationId("bar")
+                                      .Authorization(TAG_CERTIFICATE_SERIAL, serial_blob)
+                                      .Authorization(TAG_CERTIFICATE_SUBJECT, subject_der)
+                                      .Authorization(TAG_NO_AUTH_REQUIRED)
+                                      .SetDefaultValidity(),
+                              attest_key_opt, &key_blob_list[i], &attested_key_characteristics,
+                              &cert_chain_list[i]));
+
+        AuthorizationSet hw_enforced = HwEnforcedAuthorizations(attested_key_characteristics);
+        AuthorizationSet sw_enforced = SwEnforcedAuthorizations(attested_key_characteristics);
+        EXPECT_TRUE(verify_attestation_record("foo", "bar", sw_enforced, hw_enforced, SecLevel(),
+                                              cert_chain_list[i][0].encodedCertificate));
+
+        if (i > 0) {
+            /*
+             * The first key is attestated with factory chain, but all the rest of the keys are
+             * not supposed to be returned in attestation certificate chains.
+             */
+            EXPECT_FALSE(ChainSignaturesAreValid(cert_chain_list[i]));
+
+            // Appending the attest_key chain to the attested_key_chain should yield a valid chain.
+            cert_chain_list[i].insert(cert_chain_list[i].end(),        //
+                                      cert_chain_list[i - 1].begin(),  //
+                                      cert_chain_list[i - 1].end());
+        }
+
+        EXPECT_TRUE(ChainSignaturesAreValid(cert_chain_list[i]));
+        EXPECT_GT(cert_chain_list[i].size(), i + 1);
+        verify_subject_and_serial(cert_chain_list[i][0], serial_int, subject, false);
+    }
+
+    for (int i = 0; i < chain_size; i++) {
+        CheckedDeleteKey(&key_blob_list[i]);
+    }
+}
+
+/*
+ * AttestKeyTest.AlternateAttestKeyChaining
+ *
+ * This test creates a chain of multiple attest keys, in the order Ec - RSA - Ec - RSA ....
+ * Each attest key is used to sign the next attest key, with the last attest key signed by
+ * the factory chain. This is to verify different algorithms of attest keys can
+ * cross sign each other and be chained together.
+ */
+TEST_P(AttestKeyTest, AlternateAttestKeyChaining) {
+    const int chain_size = 6;
+    vector<vector<uint8_t>> key_blob_list(chain_size);
+    vector<vector<Certificate>> cert_chain_list(chain_size);
+
+    for (int i = 0; i < chain_size; i++) {
+        string sub = "Alt attest key chaining ";
+        char index = '1' + i;
+        string subject = sub + index;
+        vector<uint8_t> subject_der(make_name_from_str(subject));
+
+        uint64_t serial_int = 90000000 + i;
+        vector<uint8_t> serial_blob(build_serial_blob(serial_int));
+
+        vector<KeyCharacteristics> attested_key_characteristics;
+        AttestationKey attest_key;
+        optional<AttestationKey> attest_key_opt;
+
+        if (i > 0) {
+            attest_key.issuerSubjectName = make_name_from_str(sub + (char)(index - 1));
+            attest_key.keyBlob = key_blob_list[i - 1];
+            attest_key_opt = attest_key;
+        }
+
+        if ((i & 0x1) == 1) {
+            EXPECT_EQ(ErrorCode::OK,
+                      GenerateKey(AuthorizationSetBuilder()
+                                          .EcdsaSigningKey(224)
+                                          .AttestKey()
+                                          .AttestationChallenge("foo")
+                                          .AttestationApplicationId("bar")
+                                          .Authorization(TAG_CERTIFICATE_SERIAL, serial_blob)
+                                          .Authorization(TAG_CERTIFICATE_SUBJECT, subject_der)
+                                          .Authorization(TAG_NO_AUTH_REQUIRED)
+                                          .SetDefaultValidity(),
+                                  attest_key_opt, &key_blob_list[i], &attested_key_characteristics,
+                                  &cert_chain_list[i]));
+        } else {
+            EXPECT_EQ(ErrorCode::OK,
+                      GenerateKey(AuthorizationSetBuilder()
+                                          .RsaSigningKey(2048, 65537)
+                                          .AttestKey()
+                                          .AttestationChallenge("foo")
+                                          .AttestationApplicationId("bar")
+                                          .Authorization(TAG_CERTIFICATE_SERIAL, serial_blob)
+                                          .Authorization(TAG_CERTIFICATE_SUBJECT, subject_der)
+                                          .Authorization(TAG_NO_AUTH_REQUIRED)
+                                          .SetDefaultValidity(),
+                                  attest_key_opt, &key_blob_list[i], &attested_key_characteristics,
+                                  &cert_chain_list[i]));
+        }
+
+        AuthorizationSet hw_enforced = HwEnforcedAuthorizations(attested_key_characteristics);
+        AuthorizationSet sw_enforced = SwEnforcedAuthorizations(attested_key_characteristics);
+        EXPECT_TRUE(verify_attestation_record("foo", "bar", sw_enforced, hw_enforced, SecLevel(),
+                                              cert_chain_list[i][0].encodedCertificate));
+
+        if (i > 0) {
+            /*
+             * The first key is attestated with factory chain, but all the rest of the keys are
+             * not supposed to be returned in attestation certificate chains.
+             */
+            EXPECT_FALSE(ChainSignaturesAreValid(cert_chain_list[i]));
+
+            // Appending the attest_key chain to the attested_key_chain should yield a valid chain.
+            cert_chain_list[i].insert(cert_chain_list[i].end(),        //
+                                      cert_chain_list[i - 1].begin(),  //
+                                      cert_chain_list[i - 1].end());
+        }
+
+        EXPECT_TRUE(ChainSignaturesAreValid(cert_chain_list[i]));
+        EXPECT_GT(cert_chain_list[i].size(), i + 1);
+        verify_subject_and_serial(cert_chain_list[i][0], serial_int, subject, false);
+    }
+
+    for (int i = 0; i < chain_size; i++) {
+        CheckedDeleteKey(&key_blob_list[i]);
+    }
+}
+
 TEST_P(AttestKeyTest, AllEcCurves) {
     for (auto curve : ValidCurves()) {
         /*
diff --git a/security/keymint/aidl/vts/functional/KeyMintAidlTestBase.cpp b/security/keymint/aidl/vts/functional/KeyMintAidlTestBase.cpp
index 64ef066..6202a8b 100644
--- a/security/keymint/aidl/vts/functional/KeyMintAidlTestBase.cpp
+++ b/security/keymint/aidl/vts/functional/KeyMintAidlTestBase.cpp
@@ -1142,7 +1142,10 @@
         string cert_issuer = x509NameToStr(X509_get_issuer_name(key_cert.get()));
         string signer_subj = x509NameToStr(X509_get_subject_name(signing_cert.get()));
         if (cert_issuer != signer_subj) {
-            return AssertionFailure() << "Cert " << i << " has wrong issuer.\n" << cert_data.str();
+            return AssertionFailure() << "Cert " << i << " has wrong issuer.\n"
+                                      << " Signer subject is " << signer_subj
+                                      << " Issuer subject is " << cert_issuer << endl
+                                      << cert_data.str();
         }
     }