Secure end-to-end communication is becoming increasingly important as more private and sensitive data is transferred on the Internet. Unfortunately, today’s SSL deployment is largely limited to security or privacycritical domains. The low adoption rate is mainly attributed to the heavy cryptographic computation overhead on the server side, and the cost of good privacy on the Internet is tightly bound to expensive hardware SSL accelerators in practice. In this paper we present high-performance SSL acceleration using commodity processors. First, we show that modern graphics processing units (GPUs) can be easily converted to general-purpose SSL accelerators. By exploiting the massive computing parallelism of GPUs, we accelerate SSL cryptographic operations beyond what state-of-the-art CPUs provide. Second, we build a transparent SSL proxy, SSLShader, that carefully leverages the trade-offs of recent hardware features such as AES-NI and NUMA and achieves both high throughput and low latency. In our evaluation, the GPU implementation of RSA shows a factor of 22.6 to 31.7 improvement over the fastest CPU implementation. SSLShader achieves 29K transactions per second for small files while it transfers large files at 13 Gbps on a commodity server machine. These numbers are comparable to high-end commercial SSL appliances at a fraction of their price.

Abstract—Denial of Service (DoS) attacks aiming to exhaust the resources of a server by overwhelming it with bogus requests have become a serious threat. Especially protocols that rely on public key cryptography and perform expensive authentication handshakes may be an easy target. A well-known countermeasure against DoS attacks are client puzzles. The victimized server demands from the clients to commit computing resources before it processes their requests. To get service, a client must solve a cryptographic puzzle and submit the right solution. Existing client puzzle schemes have some drawbacks. They are either parallelizable, coarse-grained or can be used only interactively. In case of interactive client puzzles where the server poses the challenge an attacker might mount a counterattack on the clients by injecting fake packets containing bogus puzzle parameters. In this paper we introduce a novel scheme for client puzzles which relies on the computation of square roots modulo a prime. Modular square root puzzles are non-parallelizable, i. e., the solution cannot be obtained faster than scheduled by distributing the puzzle to multiple machines or CPU cores, and they can be employed both interactively and non-interactively. Our puzzles provide polynomial granularity and compact solution and verification functions. Benchmark results demonstrate the feasibility of our approach to mitigate DoS attacks on hosts in 1 or even 10 GBit networks. In addition, we show how to raise the efficiency of our puzzle scheme by introducing a bandwidth-based cost factor for the client. Keywords—client puzzles, Denial of Service (DoS), network protocols, authentication, computational puzzles

Abstract. Graphics processing units (GPUs) have become popular devices for accelerating general purpose computing. In recent years there has been a surge in research involving the use of GPUs as cryptographic accelerators. Research has shown that contemporary GPU architectures can achieve higher throughput in the context of both symmetric and asymmetric key cryptography than a traditional CPU. Despite the existence of these new approaches, there remains no way for OS kernel services or userspace applications to make use of these implementations in a practical manner. To overcome this shortcoming, this paper investigates the integration of GPU accelerated cryptographic algorithms with an established service virtualisation layer within the Linux kernel, the OCF-Linux framework. This paper demonstrates that it is feasible to use a centralised kernel service to provide a standardised abstraction to GPU accelerated cryptographic functions for both kernelspace and userspace components. 1

SSL/TLS is a standard protocol for secure Internet communication. Despite its great success, today’s SSL deployment is largely limited to security-critical domains. The low adoption rate of SSL is mainly due to high computation overhead on the server side. In this paper, we propose Graphics Processing Units (GPUs) as a new source of computing power to reduce the server-side overhead. We have designed and implemented an SSL proxy that opportunistically offloads cryptographic operations to GPUs. The evaluation results show that our GPU implementation of cryptographic operations, RSA, AES, and HMAC-SHA1, achieves high throughput while keeping the latency low. The SSL proxy significantly boosts the throughput of SSL transactions, handling 25.8K SSL transactions per second, and has comparable response time even when overloaded.