Amazon Nova AI Challenge accelerating the field of generative AI

Inaugural global university competition focused on advancing secure, trusted AI-assisted software development.

At Amazon, responsible AI development includes partnering with leading universities to foster breakthrough research. Recognizing that many academic institutions lack the resources for large-scale studies, we're transforming the landscape with the Amazon Nova AI Challenge. While the Amazon Nova AI Challenge will explore various facets of generative AI (Gen AI), this year's challenge is centered on “Trusted AI: advancing secure, AI-assisted software development to build safer, more reliable applications.”

"This challenge is truly unique," says Dr. Ruoxi Jia, an assistant professor and faculty advisor for the Virginia Tech team. "Cutting-edge AI research typically demands access to massively trained models or open-weight models. But, unfortunately, open-weights model often don't have the right level of performance. Amazon is dramatically lowering the research barrier by giving academia unprecedented access to resources and real-world scenarios."

AI Challenge-182.jpg

AI is revolutionizing software development by automating tedious yet essential tasks, such as updating software, which frees up teams to focus on innovation. For example, by integrating Amazon Q’s code transformation capability into Amazon’s internal systems, the team was able to reduce the time it takes to upgrade a Java application to Java 17 from what is typically 50 developer-days to just a few hours. This saved an estimated equivalent of 4,500 developer-years of work and generated an estimated $260M in annualized efficiency gains. However, as AI becomes more integrated into coding processes, it will inevitably bring new security challenges. By proactively addressing these risks, trust and safety are prioritized from the start.

In a “tournament-style” format, ten university teams—five model developer (defense) teams and five red (attack) teams—are competing in four sequential tournaments to strengthen AI-based secure software development. Each defense team’s code-generating model will face all five red teams, which will probe for vulnerabilities and flaws using automated techniques. The Amazon Nova team built a custom model on AWS Trainium hardware for the challenge for enabling open, collaborative research in secure software development.

The first tournament kicked off in January 2025, with a final round being held live in June 2025. All teams will publish research papers detailing their methodologies and findings, ultimately enhancing user experience, preventing misuse, and enabling more secure application of AI to software development. The advances from the challenge will contribute to the broader field of responsible AI development in code generation and beyond.

“Research is often very solitary,” says Atharva Naik, the student lead of the Carnegie Mellon University team. “Here we’re actually competing with other research teams and trying to keep up with their advancements and out-do them in real time.” The tournament format also drives teams to implement and test their strategies quickly without getting bogged down in one solution, stresses Naik.

Amazon Nova AI Challenge

The selected teams in each category:

Model Developer teams

  • Carnegie Mellon University
  • Columbia University
  • Czech Technical University, Prague, Czech Republic
  • University of Illinois Urbana-Champaign (UIUC)
  • Virginia Tech

Red teams

  • NOVA School of Science and Technology, Lisbon, Portugal
  • Purdue University
  • University of California, Davis
  • University of Texas at Dallas
  • University of Wisconsin Madison

Organizers and participants agree that the tournament format has proved to be highly motivating. The attack and defense systems must be effective against five opposing teams, and each team will get better as they face off against different opponents in each tournament.

“We brought together the best and brightest from academia to not only compete, but collectively tackle one of the most important problems in the real-world application of generative AI – safe and secure software development,” says Rohit Prasad, SVP of Amazon Artificial General Intelligence. “We’ve designed this challenge as a unique, fast-paced tournament for accelerating academic research for practical use. In Amazon tradition, I’m looking forward to the competing teams working hard, having fun, and making some history along the way to the finals.”

"This challenge exemplifies our commitment to advancing responsible AI development and security," said Steve Schmidt, Chief Security Officer, Amazon. “By partnering with universities, we're tapping into a wellspring of fresh ideas and cultivating future AI security leaders. This initiative goes beyond theoretical research—it's about developing new ways to identify security vulnerabilities and protect against threats that can be directly applied to generative AI coding assistants. I can’t wait to see what the students invent, and to share their research.”

Each team will receive $250,000 in sponsorship, monthly AWS credits, and the chance to compete for top prizes. The winning red team and model developer team will each receive $250,000 (to be split among students), with second-place teams earning $100,000. Including stipends, $700,000 in prizes, and AWS credits, the total investment in teams exceeds $5 million.

Bringing together the best

Amazon organizers reviewed over 90 proposals to choose the final ten teams to compete in the challenge. According to Michael Johnston, an applied science leader at Amazon overseeing the science and engineering behind the challenge, it was a tough decision, and those selected had to bring a wide range of unique and practical ideas to the table. Because each team will compete against multiple opponents, they need to be ready with multiple strategies. And because their opponents will be constantly adjusting, those ideas have to show creativity and adaptability.

The challenge is inherently multi-disciplinary – situated at the intersection of responsible AI, Gen AI, security, conversational AI, and automated software development. As such it has brought together teams with expertise across multiple fields of study bringing different talents and perspectives to the competition.

From theory to practical solutions

The Amazon Nova AI Challenge encourages teams to approach problems through a more pragmatic lens than what’s often used in academic research. Virginia Tech’s Jia points out that academic literature tends to focus on theoretical problems, with a bias toward complicated solutions. That’s not what is needed here. The challenge helps frame the problem in a way that is beneficial to real people, says Jia. In her conversations with Amazon researchers, she says it’s clear that they’re not impressed by solutions that are overly complex. “They tell me they want the solution that is the simplest: one that is robust and easy to troubleshoot,” she says. “That can be eye-opening and reshapes my research philosophy a little bit.”

The teams are also accessing a level of resources not often available in academia. “We are trying new things that otherwise would be very hard on an academic budget,” says Naik. His team has generally worked with smaller datasets, and hasn’t had an opportunity to train LLMs or run larger experiments. Ondrej Kobza, student lead of the Czech Technical University team, was similarly impressed during bootcamp. “We got instant access to AWS Trainium chips, a family of AI chips purpose built by AWS for AI training and inference to deliver high performance while reducing costs. That’s really amazing, especially for a team from a small university in the Czech Republic where we don’t have the opportunity to access this powerful hardware.”

“The challenge aligns with our research interests really well,” says Professor Xiangyu Zhang of Purdue, an advisor to his school’s team. “And we do need the extra step of competition. We are attacking from all corners.”

Stay tuned for updates on the teams' progress and coverage of the finals in June 2025.

Related content

US, VA, Arlington
The Sponsored Products and Brands team at Amazon Ads is re-imagining the advertising landscape through SOTA generative AI technologies, revolutionizing how millions of customers discover products and engage with brands across Amazon.com and beyond. We are at the forefront of re-inventing advertising experiences, bridging human creativity with artificial intelligence to transform every aspect of the advertising lifecycle from ad creation and optimization to performance analysis and customer insights. We are a passionate group of innovators dedicated to developing responsible and intelligent AI technologies that balance the needs of advertisers, enhance the shopping experience, and strengthen the marketplace. If you're energized by solving complex challenges and pushing the boundaries of what's possible with AI, join us in shaping the future of advertising. The Marketplace Intelligence (MI) team is looking for an Applied Science Manager to lead a team of scientists and engineers in building production ML and bandit solutions to customize the search experience. We determine which ads to show in Amazon search, where to place them, how many ads to place, and to which customers. This helps shoppers discover new products while helping advertisers put their products in front of the right customers, aligning shoppers’, advertisers’, and Amazon’s interests. To do this, we apply a broad range of machine learning, causal inference, and optimization techniques to continuously explore, learn, and optimize the allocation and ranking of ads on the search page. We are an interdisciplinary team with a focus on customer obsession and inventing and simplifying. Our primary focus is on improving the SP experience in search by gaining a deep understanding of shopper pain points and developing new innovative solutions to address them. You’ll lead the MI Interleaving team. The Interleaving team’s mission is to personalize and contextualize SP ad allocation on the search page. We do this by modeling shopper responses to the number, placement, and quality of ads. We use online experimentation, simulation, causal modeling, and online feedback to estimate the cost of displacing organic and sponsored content. Then, we incorporate those estimates into ad allocation to deliver an efficient and customized shopping experience for shoppers and improved discoverability and sales for advertisers. You’ll own the experimentation systems, models, and online model serving infrastructure to support these solutions. This is a unique opportunity for someone who wants to have broad business impact, a direct impact on customers and the search experience, build scaled real-time LLM and ML solutions, and lead a cross-functional team. If you are interested in machine learning, bandit learning, building production systems, and leading a team to build these solutions, this role is for you. We’re looking for a leader who can help lay out the vision for the team and grow with it. Key job responsibilities * Lead a team of scientists and engineers in building scalable machine learning solutions. * Develop a vision for contextualizing and personalizing SP ads in Amazon search. * Create, develop, and drive a data-driven product strategy to define the right quantitative measures of shopper impact, using this to evaluate decisions and opportunities. * Tackle and solve challenging science and business problems that balance the interests of advertisers, shoppers, and Amazon. * Own a portfolio of pragmatic long-term investments that drive long-term growth of the ads and retail businesses. * Develop real-time LLM and ML algorithms to allocate billions of ads per day in advertising auctions. * Develop efficient algorithms for multi-objective optimization and AI control methods to find operating points for the ad marketplace then evolve them * Develop scientists and ML engineers around machine learning, economics, and optimization for Advertising.
CH, Zurich
RIVR, an Amazon company, is building Physical AI by deploying autonomous robots for real-world doorstep delivery. Operating daily in diverse urban environments, RIVR's robots continuously learn from and navigate the millions of scenarios encountered during deliveries. By owning the full stack from software. Our fleet of delivery robots operates globally today, generating vast amounts of robotic real-world data. By utilizing state-of-the-art Vision-Language-Action (VLA) models, large-scale generalist models (like Transformers), generative AI, and similar methods, we can leverage this pool of data to significantly enhance its autonomy, navigation, and manipulation skills. In this role, you will develop multi-modal models that enable robots to autonomously generate actions from demonstrations, real-time sensor data, and natural language commands. We are seeking an expert in VLA models, imitation learning, and generative AI techniques with a deep knowledge of supervised, and self-supervised learning algorithms. If you are passionate about pushing the boundaries of AI we invite you to join us in shaping the future of intelligent robotics. Key job responsibilities Develop and implement Vision-Language-Action (VLA) models, generalist robot transformers, and imitation learning algorithms (e.g., diffusion policies) to enable robots to autonomously execute complex tasks. Design, test, and refine your algorithms to meet the demands of complex real-world autonomy and navigation tasks, with a focus on spatial reasoning and generalization. Streamline the data collection and training workflow to efficiently expand model capabilities with new tasks and data sources. Collaborate with the reinforcement learning team to innovate methods that leverage both simulated and real-world data. Optimize and distill networks for real-time deployment on the edge (e.g. Nvidia Jetson Thor). Build, lead and mentor an exceptional team of software engineers. Provide expert guidance to product managers and executives for strategic decision-making. Create and maintain documentation, guidelines, and best practices to streamline knowledge sharing.
US, CA, Culver City
MULTIPLE POSITIONS AVAILABLE Employer: AMAZON.COM SERVICES LLC Offered Position: Data Scientist II Job Location: Culver City, California Job Number: AMZ10564056 Position Responsibilities: Design and implement scalable and reliable approaches to support or automate decision making throughout the business. Apply a range of data science techniques and tools combined with subject matter expertise to solve difficult business problems and cases in which the solution approach is unclear. Acquire data by building the necessary SQL / ETL queries. Import processes through various company specific interfaces for accessing Oracle, RedShift, and Spark storage systems. Build relationships with stakeholders and counterparts. Analyze data for trends and input validity by inspecting univariate distributions, exploring bivariate relationships, constructing appropriate transformations, and tracking down the source and meaning of anomalies. Build models using statistical modeling, mathematical modeling, econometric modeling, network modeling, social network modeling, natural language processing, machine learning algorithms, genetic algorithms, and neural networks. Validate models against alternative approaches, expected and observed outcome, and other business defined key performance indicators. Implement models that comply with evaluations of the computational demands, accuracy, and reliability of the relevant ETL processes at various stages of production. 40 hours / week, 8:00am-5:00pm, Salary Range: $158,681/year to $184,000/year. Amazon is a total compensation company. Dependent on the position offered, equity, sign-on payments, and other forms of compensation may be provided as part of a total compensation package, in addition to a full range of medical, financial, and/or other benefits. For more information, visit: https://www.aboutamazon.com/workplace/employee-benefits. Amazon.com is an Equal Opportunity-Affirmative Action Employer – Minority / Female / Disability / Veteran / Gender Identity / Sexual Orientation.#0000
ES, M, Madrid
At Amazon, we are committed to being the Earth’s most customer-centric company. The European International Technology group (EU INTech) owns the enhancement and delivery of Amazon’s engineering to all the varied customers and cultures of the world. We do this through a combination of partnerships with other Amazon technical teams and our own innovative new projects. You will be joining the Tools and Machine Learning (Tamale) team. As part of EU INTech, we tackle complex, high-impact problems at the intersection of e-commerce, AI, and customer experience; going well beyond traditional ML pipelines. Our work spans multiple frontiers: we build GenAI-powered data solutions, enabling scalable and cost-efficient training data generation at Amazon scale. We design and deploy agentic systems for detecting and fixing quality issues across Amazon's retail surfaces. And we develop ranking and recommendation models for Haul shopping experiences. We are looking for a passionate, talented, and inventive Scientist with a strong machine learning background to help build industry-leading machine learning solutions. We strongly value your hard work and obsession to solve complex problems on behalf of Amazon customers. Key job responsibilities We look for applied scientists who possess a wide variety of skills. As the successful applicant for this role, you will with work closely with your business partners to identify opportunities for innovation. You will apply machine learning solutions to automate manual processes, to scale existing systems and to improve catalog data quality, to name just a few. You will work with business leaders, scientists, and product managers to translate business and functional requirements into concrete deliverables, including the design, development, testing, and deployment of highly scalable distributed services. You will be part of team of scientists and engineers working on solving data quality issues at scale. You will be able to influence the scientific roadmap of the team, setting the standards for scientific excellence. You will be working with state-of-the-art models, including image to text, Multimodal LLMs and GenAI. Your work will improve the experience of millions of daily customers using Amazon in Europe and in other regions. You will have the chance to have great customer impact and continue growing in one of the most innovative companies in the world. You will learn a huge amount - and have a lot of fun - in the process!
CL, Virtual
The Central Science Team within Amazon’s People Experience and Technology org (PXTCS) uses economics, behavioral science, statistics, and machine learning to proactively identify mechanisms and process improvements which simultaneously improve Amazon and the lives, well-being, and the value of work to Amazonians. We are an interdisciplinary team, which combines the talents of science and engineering to develop and deliver solutions that measurably achieve this goal. We are looking for a Economist II who is able to provide structure around complex business problems, hone those complex problems into specific, scientific questions, and test those questions to generate insights. The ideal candidate will work with various science, engineering, operations, and analytics teams to estimate models and algorithms on large scale data, design pilots and measure their impact, and transform successful prototypes into improved policies and programs at scale. They will lead teams of researchers to produce robust, objective research results and insights which can be communicated to a broad audience inside and outside of Amazon. The ideal candidate has a PhD in Economics and deep expertise in causal inference and applied econometrics. Experience with large-scale data, proficiency in statistical programming (Python), and familiarity with machine learning methods are a plus. To be successful in this role, you should be comfortable operating with ambiguity, able to independently scope and prioritize research agendas, skilled at influencing decisions through rigorous analysis, and comfortable with using AI tools.
US, MA, Boston
Our team is involved with pre-silicon design verification for custom IP. A critical requirement of the verification flow is the requirement of legal and realistic stimulus of a custom Machine Learning Accelerator Chip. Content creation is built using formal methods that model legal behavior of the design and then solving the problem to create the specific assembly tests. The entire frame work for creating these custom tests is developed using a SMT solver and custom software code to guide the solution space into templated scenarios. This highly visible and innovative role requires the design of this solving framework and collaborating with design verification engineers, hardware architects and designers to ensure that interesting content can be created for the projects needs. Key job responsibilities Develop an understanding for a custom machine learning instruction set architecture. Model correctness of instruction streams using first order logic. Create custom API's to allow control over scheduling and randomness. Deploy algorithms to ensure concurrent code is safely constructed. Create coverage metrics to ensure solution space coverage. Use novel methods like machine learning to automate content creation. About the team Utility Computing (UC) AWS Utility Computing (UC) provides product innovations — from foundational services such as Amazon’s Simple Storage Service (S3) and Amazon Elastic Compute Cloud (EC2), to consistently released new product innovations that continue to set AWS’s services and features apart in the industry. As a member of the UC organization, you’ll support the development and management of Compute, Database, Storage, Internet of Things (Iot), Platform, and Productivity Apps services in AWS, including support for customers who require specialized security solutions for customers who require specialized security solutions for their cloud services. Annapurna Labs (our organization within AWS UC) designs silicon and software that accelerates innovation. Customers choose us to create cloud solutions that solve challenges that were unimaginable a short time ago—even yesterday. Our custom chips, accelerators, and software stacks enable us to take on technical challenges that have never been seen before, and deliver results that help our customers change the world.
IN, KA, Bengaluru
Amazon Devices is an inventive research and development company that designs and engineer high-profile devices like the Kindle family of products, Fire Tablets, Fire TV, Health Wellness, Amazon Echo & Astro products. This is an exciting opportunity to join Amazon in developing state-of-the-art techniques that bring Gen AI on edge for our consumer products. We are looking for exceptional scientists to join our Applied Science team and help develop the next generation of edge models, and optimize them while doing co-designed with custom ML HW based on a revolutionary architecture. Work hard. Have Fun. Make History. Key job responsibilities - Quantize, prune, distill, finetune Gen AI models to optimize for edge platforms - Fundamentally understand Amazon’s underlying Neural Edge Engine to invent optimization techniques - Analyze deep learning workloads and provide guidance to map them to Amazon’s Neural Edge Engine - Use first principles of Information Theory, Scientific Computing, Deep Learning Theory, Non Equilibrium Thermodynamics - Train custom Gen AI models that beat SOTA and paves path for developing production models - Collaborate closely with compiler engineers, fellow Applied Scientists, Hardware Architects and product teams to build the best ML-centric solutions for our devices - Publish in open source and present on Amazon's behalf at key ML conferences - NeurIPS, ICLR, MLSys.
IN, KA, Bengaluru
Have you ever wondered how that Amazon box with the smile arrives so quickly, where it came from, and how much it cost Amazon to deliver? The WW Amazon Logistics, Business Analytics team manages the delivery of tens of millions of products every week to Amazon's customers, achieving on-time delivery in a cost-effective manner. We are seeking an enthusiastic, customer-obsessed Research Science Manager(RSM) with strong analytical skills to join our team. This role is crucial in optimizing Amazon's vast delivery network and will have significant impact on the customer experience, particularly in the final phase of delivery. As a Research Science Manager, you will: 1. Address business challenges through building compelling cases and using data to influence change across the organization 2. Develop input and assumptions based on preexisting models to estimate costs and savings opportunities associated with varying levels of network growth and operations 3. Create metrics to measure business performance, identify root causes and trends, and prescribe action plans 4. Manage multiple high-impact projects simultaneously 5. Work with technology teams and product managers to develop new tools and systems supporting business growth 6. Communicate with and support various internal stakeholders and external audiences 7. Implement scheduling solutions, improve metrics, and develop scalable processes and tools Looking for minds with: Extensive experience in operations research and data-driven decision making Strong analytical and problem-solving skills Robust program management and research science skills Ability to work with a team and make independent decisions in ambiguous environments Customer-obsessed mindset with a focus on improving the Amazon delivery experience This role offers the autonomy to think strategically and make data-driven decisions from day one. Join us in shaping the future of e-commerce delivery and addressing the core challenges in our world-class operations space! Key job responsibilities Key job responsibilities 1. Advanced Modeling and Algorithm Development: Design and implement sophisticated machine learning models for logistics optimization Develop complex time series forecasting algorithms for demand prediction and resource allocation 2. AI and Machine Learning Integration: Architect and deploy AI-powered systems to enhance decision-making in logistics operations Implement deep learning techniques for image recognition in package sorting and handling Develop reinforcement learning algorithms for adaptive scheduling and resource management 3. Big Data Analytics and Processing: Design and implement distributed computing solutions for processing massive logistics datasets Utilize cloud computing platforms (e.g., AWS) for scalable data processing and analysis 4. AI-Driven Workflow Optimization: Design and implement AI agents for autonomous decision-making in logistics processes Create machine learning models for customer behavior analysis and personalized delivery options 5. Software Development and System Architecture: Write efficient, scalable code in languages such as Python, Java, or C++ Develop and maintain complex software systems for logistics optimization Stay at the forefront of AI and ML research Publish research findings in top-tier conferences and journals About the team We are Amazon's Last Mile Science and Analytics team, dedicated to improving e-commerce delivery. We work to optimize our vast network, forecast demand using machine learning, and enhance route efficiency. Our efforts focus on developing innovative delivery methods, applying AI to solve complex problems, and conducting geospatial analysis. We create simulations to refine processes and plan capacity effectively. Operating globally, we strive to develop adaptable solutions for diverse markets. We aim to advance logistics science, continually improving speed, efficiency, and customer satisfaction, in support of Amazon's mission to be Earth's most customer-centric company.
US, CA, Culver City
MULTIPLE POSITIONS AVAILABLE Employer: AMAZON.COM SERVICES LLC Offered Position: Applied Scientist III Job Location: Culver City, California Job Number: AMZ10564141 Position Responsibilities: Participate in the design, development, evaluation, deployment and updating of data-driven models and analytical solutions for machine learning (ML) and/or natural language (NL) applications. Develop and/or apply statistical modeling techniques (e.g. Bayesian models and deep neural networks), optimization methods, and other ML techniques to different applications in business and engineering. Routinely build and deploy ML models on available data, and run and analyze experiments in a production environment. Identify new opportunities for research in order to meet business goals. Research and implement novel ML and statistical approaches to add value to the business. Mentor junior engineers and scientists. 40 hours / week, 8:00am-5:00pm, Salary Range: $167,100/year to $226,100/year. Amazon is a total compensation company. Dependent on the position offered, equity, sign-on payments, and other forms of compensation may be provided as part of a total compensation package, in addition to a full range of medical, financial, and/or other benefits. For more information, visit: https://www.aboutamazon.com/workplace/employee-benefits. Amazon.com is an Equal Opportunity-Affirmative Action Employer – Minority / Female / Disability / Veteran / Gender Identity / Sexual Orientation.#0000
IN, KA, Bengaluru
We are looking for a talented Applied Scientist to join our team. In this role, you will design, develop, and deploy machine learning and computer vision models that solve real-world problems at scale in the Amazon grocery domain. You will work closely with engineering, product, and business teams to turn complex technical challenges into production-ready solutions, and own the model development lifecycle from experimentation through deployment. You will bring scientific rigor to every stage — from data analysis and model design to evaluation and iteration. This is a high-impact role where your models will directly improve the shopping experience for millions of customers in Amazon grocery stores. Key job responsibilities Design, train, and evaluate computer vision and machine learning models for complex grocery-domain problems including product identification, shelf perception, and in-store scene understanding — iterating rapidly from prototype to production-quality solutions Conduct rigorous exploratory data analysis to characterize domain-specific challenges (image variability, catalog gaps, label noise) and translate findings into actionable modeling decisions Own the model development lifecycle from experimentation through deployment — collaborating with software and ML engineers to ensure models meet latency, throughput, and reliability requirements at production scale Design and execute offline and online evaluation frameworks — defining metrics that capture both model performance and downstream business impact, and diagnosing failure modes to prioritize improvements Build and improve data pipelines and annotation workflows that feed model training, including active learning strategies to maximize label efficiency Communicate technical results, trade-offs, and recommendations clearly to engineering, product, and business stakeholders — connecting model behavior to customer experience outcomes Stay current with state-of-the-art research in computer vision, multimodal learning, and representation learning — evaluating and adapting promising techniques to team-specific problems Contribute to a culture of scientific rigor through reproducible experimentation, thorough documentation, peer code and design reviews, and raising the quality bar for the team A day in the life As an Applied Scientist on the GRAISE team, you'll spend your days analyzing model performance from overnight experiments, collaborating with engineers to deploy computer vision models to production, and prototyping new approaches using multimodal learning with store video and sensor data. You'll present findings to product and business stakeholders, translating technical results into actionable recommendations. Throughout the day, you'll balance rigorous scientific thinking with practical engineering constraints, knowing your work directly improves the shopping experience for millions of customers in Amazon grocery stores. About the team The GRAISE team (Grocery, Retail & In-Store Experience) within World Wide Grocery Store Tech (WWGST) builds foundational AI and machine learning systems that power Amazon's in-store grocery technologies. We develop domain-specific models that solve uniquely complex challenges in grocery — from smart shopping carts and inventory intelligence to personalization and store operations. Our mission is to create technology which makes grocery shopping more convenient, economical, personalized, and enjoyable for customers while empowering retailers with operational efficiency