diff --git a/gatekeeper/aidl/software/SharedSecret.cpp b/gatekeeper/aidl/software/SharedSecret.cpp
new file mode 100644
index 0000000..f693700
--- /dev/null
+++ b/gatekeeper/aidl/software/SharedSecret.cpp
@@ -0,0 +1,131 @@
+/*
+ * Copyright 2024, 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 "SharedSecret.h"
+
+#include <algorithm>
+#include <cstring>
+#include <mutex>
+#include <vector>
+
+#include <openssl/rand.h>
+
+#include <KeyMintUtils.h>
+#include <aidl/android/hardware/security/sharedsecret/BnSharedSecret.h>
+#include <aidl/android/hardware/security/sharedsecret/SharedSecretParameters.h>
+#include <android-base/logging.h>
+#include <keymaster/android_keymaster_messages.h>
+#include <keymaster/android_keymaster_utils.h>
+#include <keymaster/km_openssl/ckdf.h>
+#include <keymaster/km_openssl/hmac.h>
+
+namespace aidl::android::hardware::security::sharedsecret {
+
+::ndk::ScopedAStatus SoftSharedSecret::getSharedSecretParameters(
+        SharedSecretParameters* out_params) {
+    std::lock_guard lock(mutex_);
+    if (seed_.empty()) {
+        seed_.resize(32, 0);
+    }
+    out_params->seed = seed_;
+    if (nonce_.empty()) {
+        nonce_.resize(32, 0);
+        RAND_bytes(nonce_.data(), 32);
+    }
+    out_params->nonce = nonce_;
+    LOG(INFO) << "Presented shared secret parameters with seed size " << out_params->seed.size()
+              << " and nonce size " << out_params->nonce.size();
+    return ::ndk::ScopedAStatus::ok();
+}
+
+::ndk::ScopedAStatus SoftSharedSecret::computeSharedSecret(
+        const std::vector<SharedSecretParameters>& params, std::vector<uint8_t>* sharing_check) {
+    std::lock_guard lock(mutex_);
+    LOG(INFO) << "Computing shared secret";
+    // Reimplemented based on SoftKeymasterEnforcement, which does not expose
+    // enough functionality to satisfy the GateKeeper interface
+    keymaster::KeymasterKeyBlob key_agreement_key;
+    if (key_agreement_key.Reset(32) == nullptr) {
+        LOG(ERROR) << "key agreement key memory allocation failed";
+        return keymint::km_utils::kmError2ScopedAStatus(KM_ERROR_MEMORY_ALLOCATION_FAILED);
+    }
+    // Matching:
+    // - kFakeAgreementKey in system/keymaster/km_openssl/soft_keymaster_enforcement.cpp
+    // - Keys::kak in hardware/interfaces/security/keymint/aidl/default/ta/soft.rs
+    std::memset(key_agreement_key.writable_data(), 0, 32);
+    keymaster::KeymasterBlob label((uint8_t*)KEY_AGREEMENT_LABEL, strlen(KEY_AGREEMENT_LABEL));
+    if (label.data == nullptr) {
+        LOG(ERROR) << "label memory allocation failed";
+        return keymint::km_utils::kmError2ScopedAStatus(KM_ERROR_MEMORY_ALLOCATION_FAILED);
+    }
+
+    static_assert(sizeof(keymaster_blob_t) == sizeof(keymaster::KeymasterBlob));
+
+    bool found_mine = false;
+    std::vector<keymaster::KeymasterBlob> context_blobs;
+    for (const auto& param : params) {
+        auto& seed_blob = context_blobs.emplace_back();
+        if (seed_blob.Reset(param.seed.size()) == nullptr) {
+            LOG(ERROR) << "seed memory allocation failed";
+            return keymint::km_utils::kmError2ScopedAStatus(KM_ERROR_MEMORY_ALLOCATION_FAILED);
+        }
+        std::copy(param.seed.begin(), param.seed.end(), seed_blob.writable_data());
+        auto& nonce_blob = context_blobs.emplace_back();
+        if (nonce_blob.Reset(param.nonce.size()) == nullptr) {
+            LOG(ERROR) << "Nonce memory allocation failed";
+            return keymint::km_utils::kmError2ScopedAStatus(KM_ERROR_MEMORY_ALLOCATION_FAILED);
+        }
+        std::copy(param.nonce.begin(), param.nonce.end(), nonce_blob.writable_data());
+        if (param.seed == seed_ && param.nonce == nonce_) {
+            found_mine = true;
+        }
+    }
+    if (!found_mine) {
+        LOG(ERROR) << "Did not receive my own shared secret parameter back";
+        return keymint::km_utils::kmError2ScopedAStatus(KM_ERROR_INVALID_ARGUMENT);
+    }
+    auto context_blobs_ptr = reinterpret_cast<keymaster_blob_t*>(context_blobs.data());
+    if (hmac_key_.Reset(32) == nullptr) {
+        LOG(ERROR) << "hmac key allocation failed";
+        return keymint::km_utils::kmError2ScopedAStatus(KM_ERROR_MEMORY_ALLOCATION_FAILED);
+    }
+    auto error = keymaster::ckdf(key_agreement_key, label, context_blobs_ptr, context_blobs.size(),
+                                 &hmac_key_);
+    if (error != KM_ERROR_OK) {
+        LOG(ERROR) << "CKDF failed";
+        return keymint::km_utils::kmError2ScopedAStatus(error);
+    }
+
+    keymaster::HmacSha256 hmac_impl;
+    if (!hmac_impl.Init(hmac_key_.key_material, hmac_key_.key_material_size)) {
+        LOG(ERROR) << "hmac initialization failed";
+        return ::ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_STATE);
+    }
+    sharing_check->clear();
+    sharing_check->resize(32, 0);
+    if (!hmac_impl.Sign((const uint8_t*)KEY_CHECK_LABEL, strlen(KEY_CHECK_LABEL),
+                        sharing_check->data(), sharing_check->size())) {
+        return ::ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_STATE);
+    }
+    return ::ndk::ScopedAStatus::ok();
+}
+
+keymaster::KeymasterKeyBlob SoftSharedSecret::HmacKey() const {
+    std::lock_guard lock(mutex_);
+    return hmac_key_;
+}
+
+}  // namespace aidl::android::hardware::security::sharedsecret