diff --git a/identity/aidl/default/WritableIdentityCredential.cpp b/identity/aidl/default/WritableIdentityCredential.cpp
index ba2062d..89f7f35 100644
--- a/identity/aidl/default/WritableIdentityCredential.cpp
+++ b/identity/aidl/default/WritableIdentityCredential.cpp
@@ -16,6 +16,9 @@
 
 #define LOG_TAG "WritableIdentityCredential"
 
+#include "WritableIdentityCredential.h"
+#include "IdentityCredentialStore.h"
+
 #include <android/hardware/identity/support/IdentityCredentialSupport.h>
 
 #include <android-base/logging.h>
@@ -23,6 +26,8 @@
 #include <cppbor/cppbor.h>
 #include <cppbor/cppbor_parse.h>
 
+#include <utility>
+
 #include "IdentityCredentialStore.h"
 #include "Util.h"
 #include "WritableIdentityCredential.h"
@@ -33,26 +38,6 @@
 using namespace ::android::hardware::identity;
 
 bool WritableIdentityCredential::initialize() {
-    optional<vector<uint8_t>> keyPair = support::createEcKeyPair();
-    if (!keyPair) {
-        LOG(ERROR) << "Error creating credentialKey";
-        return false;
-    }
-
-    optional<vector<uint8_t>> pubKey = support::ecKeyPairGetPublicKey(keyPair.value());
-    if (!pubKey) {
-        LOG(ERROR) << "Error getting public part of credentialKey";
-        return false;
-    }
-    credentialPubKey_ = pubKey.value();
-
-    optional<vector<uint8_t>> privKey = support::ecKeyPairGetPrivateKey(keyPair.value());
-    if (!privKey) {
-        LOG(ERROR) << "Error getting private part of credentialKey";
-        return false;
-    }
-    credentialPrivKey_ = privKey.value();
-
     optional<vector<uint8_t>> random = support::getRandom(16);
     if (!random) {
         LOG(ERROR) << "Error creating storageKey";
@@ -63,88 +48,54 @@
     return true;
 }
 
-// TODO: use |attestationApplicationId| and |attestationChallenge| and also
-//       ensure the returned certificate chain satisfy the requirements listed in
-//       the docs for IWritableIdentityCredential::getAttestationCertificate()
-//
+// This function generates the attestation certificate using the passed in
+// |attestationApplicationId| and |attestationChallenge|.  It will generate an
+// attestation certificate with current time and expires one year from now.  The
+// certificate shall contain all values as specified in hal.
 ndk::ScopedAStatus WritableIdentityCredential::getAttestationCertificate(
-        const vector<int8_t>& /*attestationApplicationId*/,
-        const vector<int8_t>& /*attestationChallenge*/, vector<Certificate>* outCertificateChain) {
-    // For now, we dynamically generate an attestion key on each and every
-    // request and use that to sign CredentialKey. In a real implementation this
-    // would look very differently.
-    optional<vector<uint8_t>> attestationKeyPair = support::createEcKeyPair();
-    if (!attestationKeyPair) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_FAILED, "Error creating attestationKey"));
-    }
-
-    optional<vector<uint8_t>> attestationPubKey =
-            support::ecKeyPairGetPublicKey(attestationKeyPair.value());
-    if (!attestationPubKey) {
+        const vector<int8_t>& attestationApplicationId,  //
+        const vector<int8_t>& attestationChallenge,      //
+        vector<Certificate>* outCertificateChain) {
+    if (!credentialPrivKey_.empty() || !credentialPubKey_.empty() || !certificateChain_.empty()) {
         return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
                 IIdentityCredentialStore::STATUS_FAILED,
-                "Error getting public part of attestationKey"));
+                "Error attestation certificate previously generated"));
     }
 
-    optional<vector<uint8_t>> attestationPrivKey =
-            support::ecKeyPairGetPrivateKey(attestationKeyPair.value());
-    if (!attestationPrivKey) {
+    vector<uint8_t> challenge(attestationChallenge.begin(), attestationChallenge.end());
+    vector<uint8_t> appId(attestationApplicationId.begin(), attestationApplicationId.end());
+
+    optional<std::pair<vector<uint8_t>, vector<vector<uint8_t>>>> keyAttestationPair =
+            support::createEcKeyPairAndAttestation(challenge, appId);
+    if (!keyAttestationPair) {
+        LOG(ERROR) << "Error creating credentialKey and attestation";
         return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
                 IIdentityCredentialStore::STATUS_FAILED,
-                "Error getting private part of attestationKey"));
+                "Error creating credentialKey and attestation"));
     }
 
-    string serialDecimal;
-    string issuer;
-    string subject;
-    time_t validityNotBefore = time(nullptr);
-    time_t validityNotAfter = validityNotBefore + 365 * 24 * 3600;
+    vector<uint8_t> keyPair = keyAttestationPair.value().first;
+    certificateChain_ = keyAttestationPair.value().second;
 
-    // First create a certificate for |credentialPubKey| which is signed by
-    // |attestationPrivKey|.
-    //
-    serialDecimal = "0";  // TODO: set serial to |attestationChallenge|
-    issuer = "Android Open Source Project";
-    subject = "Android IdentityCredential CredentialKey";
-    optional<vector<uint8_t>> credentialPubKeyCertificate = support::ecPublicKeyGenerateCertificate(
-            credentialPubKey_, attestationPrivKey.value(), serialDecimal, issuer, subject,
-            validityNotBefore, validityNotAfter);
-    if (!credentialPubKeyCertificate) {
+    optional<vector<uint8_t>> pubKey = support::ecKeyPairGetPublicKey(keyPair);
+    if (!pubKey) {
         return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
                 IIdentityCredentialStore::STATUS_FAILED,
-                "Error creating certificate for credentialPubKey"));
+                "Error getting public part of credentialKey"));
     }
+    credentialPubKey_ = pubKey.value();
 
-    // This is followed by a certificate for |attestationPubKey| self-signed by
-    // |attestationPrivKey|.
-    serialDecimal = "0";  // TODO: set serial
-    issuer = "Android Open Source Project";
-    subject = "Android IdentityCredential AttestationKey";
-    optional<vector<uint8_t>> attestationKeyCertificate = support::ecPublicKeyGenerateCertificate(
-            attestationPubKey.value(), attestationPrivKey.value(), serialDecimal, issuer, subject,
-            validityNotBefore, validityNotAfter);
-    if (!attestationKeyCertificate) {
+    optional<vector<uint8_t>> privKey = support::ecKeyPairGetPrivateKey(keyPair);
+    if (!privKey) {
         return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
                 IIdentityCredentialStore::STATUS_FAILED,
-                "Error creating certificate for attestationPubKey"));
+                "Error getting private part of credentialKey"));
     }
+    credentialPrivKey_ = privKey.value();
 
-    // Concatenate the certificates to form the chain.
-    vector<uint8_t> certificateChain;
-    certificateChain.insert(certificateChain.end(), credentialPubKeyCertificate.value().begin(),
-                            credentialPubKeyCertificate.value().end());
-    certificateChain.insert(certificateChain.end(), attestationKeyCertificate.value().begin(),
-                            attestationKeyCertificate.value().end());
-
-    optional<vector<vector<uint8_t>>> splitCertChain =
-            support::certificateChainSplit(certificateChain);
-    if (!splitCertChain) {
-        return ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
-                IIdentityCredentialStore::STATUS_FAILED, "Error splitting certificate chain"));
-    }
+    // convert from vector<vector<uint8_t>>> to vector<Certificate>*
     *outCertificateChain = vector<Certificate>();
-    for (const vector<uint8_t>& cert : splitCertChain.value()) {
+    for (const vector<uint8_t>& cert : certificateChain_) {
         Certificate c = Certificate();
         c.encodedCertificate = byteStringToSigned(cert);
         outCertificateChain->push_back(std::move(c));