OpenBSD Cryptographic Framework
The OpenBSD Cryptographic Framework is a service virtualization layer for the uniform management of cryptographic hardware by an operating system. It is part of the OpenBSD Project, having been included in the operating system since OpenBSD 2.8. Like other OpenBSD projects such as OpenSSH, it has been ported to other systems based on Berkeley Unix such as FreeBSD and NetBSD, and to Solaris and Linux. One of the Linux ports is supported by Intel for use with its proprietary cryptographic software and hardware to provide hardware-accelerated SSL encryption for the open source Apache HTTP Server.
Background
Cryptography is computationally intensive and is used in many different contexts. Software implementations often serve as a bottleneck to information flow or increase network latency. Specialist hardware such as cryptographic accelerators can mitigate the bottleneck problem by introducing parallelism. Certain kinds of hardware, hardware [random number generator]s, can also produce randomness more reliably than a pseudo-random software algorithm by exploiting the entropy of natural events.Unlike graphics applications such as games and film processing where similar hardware accelerators are in common use and have strong operating system support, the use of hardware in cryptography has had relatively low uptake. By the late 1990s, there was a need for a uniform operating system layer to mediate between cryptographic hardware and application software that used it. The lack of this layer led to the production of applications that were hard-coded to work with one or a very small range of cryptographic accelerators.
The OpenBSD Project, which has a history of integrating strong, carefully audited cryptography into its operating system's core, produced a framework for the provision of cryptographic hardware acceleration as an operating system service.
/dev/crypto
Application-level support is provided through the pseudo-device, which provides access to the hardware drivers through a standard ioctl interface. This simplifies the writing of applications and removes the need for the application programmer to understand the operational details of the actual hardware that will be used. was removed in OpenBSD 5.7, having been superseded by the suite of syscalls.Implications for other subsystems
The OpenBSD implementation of IPsec, the packet-level encryption protocol, was altered so that packets can be decoded in batches, which improves throughput. One rationale for this is to maximize efficiency of hardware usage—larger batches reduce the bus transmission overhead—but in practice the IPsec developers have found that this strategy improves the efficiency even of software implementations.Many Intel firmware hubs on i386 motherboards provide a hardware random number generator, and where possible this facility is used to provide entropy in IPsec.
Because OpenSSL uses the OCF, systems with hardware that supports the RSA, DH, or DSA cryptographic protocols will automatically use the hardware without any modification of the software.