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Build a Secure File Transfer System Using AWS S3 and KMS

Create a cloud-based solution for secure file upload, encrypted storage, and authorized access using AWS S3 and AWS Key Management Service (KMS).

Why Secure File Transfer Matters

In today’s cloud-native world, businesses handle sensitive documents like contracts, medical records, and intellectual property that must be protected in transit and at rest. Using AWS S3 with KMS encryption ensures end-to-end data protection with fine-grained access control.

Project Objectives

Enable users to upload and download files through a secure web interface. All files are encrypted using customer-managed keys in AWS KMS. Access is controlled via IAM roles or signed URLs, with full audit logs and version control.

Key Features to Implement

Encrypted File Uploads

Use AWS S3 with server-side encryption (SSE-KMS) to store files securely with KMS-managed keys.

Access Control & Signed URLs

Generate pre-signed URLs for authenticated download access with limited-time validity.

Audit Logs & Versioning

Enable object versioning and CloudTrail logging to monitor upload, download, and deletion events.

Role-Based Permissions

Restrict access using AWS IAM policies so only authorized users can upload/view/download files.

System Architecture Overview

Users upload files through a frontend interface, which are sent to a backend API. The backend uses AWS SDK to upload to S3 using SSE-KMS. Signed URLs are generated for download access. CloudTrail tracks every file event, while KMS handles encryption key lifecycle.

  • Storage: AWS S3 with server-side encryption (SSE-KMS)
  • Encryption: AWS Key Management Service (KMS) with custom key policies
  • Authentication: Cognito / IAM roles / API Gateway + Lambda auth
  • Frontend: React.js + file input + progress bar UI
  • Logging: AWS CloudTrail and S3 access logs
Recommended Tech Stack

Frontend

React.js, file-upload components, Toast notifications, and responsive UI

Backend

Node.js or Python Flask with AWS SDK to manage file uploads and signed URL generation

AWS Services

S3 for storage, KMS for encryption, IAM for access control, CloudTrail for audit logging

Security & Access

Pre-signed URLs, HTTPS uploads, and JWT-based authentication with Cognito

Development Steps

1. Create S3 Bucket and Enable Encryption

Set up an S3 bucket with SSE-KMS encryption and enable versioning and logging.

2. Configure KMS Key

Create a customer-managed key in KMS and set usage policies for specific IAM roles.

3. Build File Upload & Download APIs

Use AWS SDK to upload encrypted files and generate signed URLs for download.

4. Build the Frontend UI

Create upload components with file progress, success/error alerts, and file previews.

5. Implement Access Control & Logging

Use IAM policies to limit access and set up CloudTrail + S3 access logging for auditing.

Helpful References & Docs

Build a Secure and Auditable File Sharing System

Ensure file security and compliance by combining AWS S3 storage with encryption, fine-grained access, and traceable audit logs.

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