ECRYPT NoE

estreamtesting@ecrypt.eu.org

2005-11-01 1.0 2005-11-01 cdecanni first public version 0.9 2005-09-26 cdecanni first draft This document describes the &estream; testing framework and provides guidelines on how to write and submit optimized code.

One of the requirements imposed on all eSTREAM stream cipher submissions was that they should be demonstrably superior to the AES in at least one significant aspect. An aspect which is particularly significant for Profile I candidates is software performance. Software performance can be measured in many different ways, and in order to make comparisons as fair as possible, eSTREAM has decided to develop a testing framework. The framework has two objectives: assuring that all stream cipher proposals are submitted to the same tests under the same circumstances automating the test procedure as much as possible such that new optimized implementations can be included and tested with as little effort as possible. This second goal requires some cooperation from the submitters of optimized code, and the purpose of this document is to provide guidelines on how to write code that can easily be integrated in the testing framework.

&ecrypt; is a Network of Excellence within the Information Societies Technology (&ist;) Programme of the European Commission. The information in this note is provided as is, and no guarantee or warranty is given or implied that the information is fit for any particular purpose. The user thereof uses the information at his or her sole risk and liability.

Feedback is most certainly welcome for this document. Send your additions, comments and criticisms to the following email address : estreamtesting@ecrypt.eu.org.

The testing framework consists of a collection of scripts and C-code which test three aspects of the submitted code: API compliance, correctness, and performance. Many of these tests have been borrowed from the &nessie; Test Suite.

The eSTREAM API is specified in the files &ecrypt-sync.h; and &ecrypt-sync-ae.h;. The framework verifies whether the code complies to this API by performing the following tests: It checks that the code provides the necessary interfaces, i.e., that it compiles and links correctly with the test code (&ecrypt-test.c;). It checks that the ECRYPT_KEYSIZE(i) and ECRYPT_MAXKEYSIZE macros allow key sizes to be enumerated as specified by the API. Idem for IV and MAC sizes. It checks that calls to the same functions with the same parameters produce the same results, no matter how they are interleaved. When this test fails, this is often an indication that the code stores data in static variables, or that it uses uninitialized variables. It checks that the incremental encryption functions ECRYPT_encrypt_blocks and ECRYPT_encrypt_bytes produce the same ciphertext as ECRYPT_encrypt_packet when fed with the same plaintext. It also verifies that this ciphertext decrypts to the original plaintext.

The correctness of the code on different platforms is verified by generating and comparing test vectors. For convenience, eSTREAM has chosen to use the same format as the NESSIE test vectors. The test vectors currently included in the testing framework were generated by eSTREAM and still need to be verified by the designers.

Stream ciphers can be deployed in various situations, each imposing specific requirements on the efficiency of the primitive. Hence, defining a small set of performance criteria which reflects all relevant implementation properties of a stream cipher is not an easy task. In the current version of the framework, eSTREAM has limited itself to four performance measures. More detailed tests might be added in the future, though. This is where stream ciphers have the biggest potential advantage over block ciphers, and hence this figure is likely to be the most important criterion in many applications. The testing framework measures the encryption rate by encrypting a long stream in chunks of about 4KB using the ECRYPT_encrypt_blocks function. The encryption speed, in cycles/byte, is calculated by measuring the number of bytes encrypted in 250 µsec. Note that the time to setup the key or the IV is not considered in this test. While a block cipher is likely to be a better choice when encrypting very short packets, it is still interesting to determine at which length a stream cipher starts to take the lead. Moreover, stream ciphers whose encryption speeds do not deteriorate too much for small packets could have a distinct advantage in applications which use a wide range of packet sizes. The packet encryption rate is measured by applying the ECRYPT_encrypt_packet function to packets of different lengths. Each call to ECRYPT_encrypt_packet includes a separate IV setup and, if authenticated encryption is supported, a MAC finalization step. The packet lengths (40, 576, and 1500 bytes) were chosen to be representative for the traffic seen on the Internet . When an application needs to encrypt many streams in parallel on a single processor, its performance will not only depend on the encryption speed of the cipher, but also on the time spent switching from one session to another. This overhead is typically determined by the number of bytes of ECRYPT_ctx that need to be stored or restored during each context switch. In order to build a picture of the agility of the different submissions, the testing framework performs the following test: it first initiates a large number of sessions (filling 16MB of RAM with ECRYPT_ctx structures), and then encrypts streams of plaintext in short blocks of around 256 bytes using ECRYPT_encrypt_blocks, each time jumping from one session to another. The last test in the testing framework separately measures the efficiency of the key setup (ECRYPT_keysetup) and the IV setup (ECRYPT_ivsetup). Given that each call to ECRYPT_AE_ivsetup comes together with a call to ECRYPT_AE_finalize, both functions are benchmarked together in case of authenticated stream ciphers. This is probably the least critical of the four tests, considering that the efficiency of the IV setup is already reflected in the packet encryption rate, and that the time for the key setup will typically be negligible compared to the work needed to generate and exchange the key. The different tests are illustrated below with an example for SNOW 2.0. The latest results for all submissions, measured by eSTREAM on various platforms, can be found in . Primitive Name: SNOW-2.0 ======================== Profile: SW Key size: 128 bits IV size: 128 bits CPU speed: 1694.8 MHz Cycles are measured using RDTSC instruction Testing memory requirements: Size of ECRYPT_ctx: 108 bytes Testing stream encryption speed: Encrypted 22 blocks of 4096 bytes (under 1 keys, 22 blocks/key) Total time: 415015 clock ticks (244.87 usec) Encryption speed (cycles/byte): 4.61 Encryption speed (Mbps): 2943.95 Testing packet encryption speed: Encrypted 350 packets of 40 bytes (under 10 keys, 35 packets/key) Total time: 411499 clock ticks (242.80 usec) Encryption speed (cycles/packet): 1175.71 Encryption speed (cycles/byte): 29.39 Encryption speed (Mbps): 461.29 Overhead: 538.2% Encrypted 120 packets of 576 bytes (under 10 keys, 12 packets/key) Total time: 416341 clock ticks (245.66 usec) Encryption speed (cycles/packet): 3469.51 Encryption speed (cycles/byte): 6.02 Encryption speed (Mbps): 2250.95 Overhead: 30.8% Encrypted 50 packets of 1500 bytes (under 1 keys, 50 packets/key) Total time: 395528 clock ticks (233.38 usec) Encryption speed (cycles/packet): 7910.56 Encryption speed (cycles/byte): 5.27 Encryption speed (Mbps): 2570.96 Overhead: 14.5% Weighted average (Simple Imix): Encryption speed (cycles/byte): 7.35 Encryption speed (Mbps): 1844.62 Overhead: 59.6% Testing key setup speed: Did 7000 key setups (under 10 keys, 700 setups/key) Total time: 446655 clock ticks (263.54 usec) Key setup speed (cycles/setup): 63.81 Key setup speed (setups/second): 26561211.67 Testing IV setup speed: Did 500 IV setups (under 10 keys, 50 setups/key) Total time: 397912 clock ticks (234.78 usec) IV setup speed (cycles/setup): 795.82 IV setup speed (setups/second): 2129634.19 Testing key agility: Encrypted 270 blocks of 256 bytes (each time switching contexts) Total time: 412653 clock ticks (243.48 usec) Encryption speed (cycles/byte): 5.97 Encryption speed (Mbps): 2271.07 Overhead: 29.6% End of performance measurements

A tarball of the latest version of the testing framework can always be downloaded from ECRYPT's SVN repository. This repository contains the most recent implementations of all stream cipher candidates, together with test vectors, test scripts, and a few benchmark ciphers (AES in CTR mode, RC4, SNOW 2.0). The scripts expect a shell compatible with GNU Bash, system utilities compatible with GNU Coreutils, and one (or more) ANSI C compiler(s). The following sections discuss how these requirements can be fulfilled on various platforms.

The easiest way to run the testing framework on a x86 platform is to download eSTREAM's bootable Live CD. The CD allows the framework to run without any installation and without affecting the existing configuration on the host machine in any way. The Live CD is based on Ubuntu and includes: a stripped-down version of Ubuntu 5.04. a working copy of the testing framework. different versions of GCC (2.95, 3.3, 3.4, and 4.0). Intel C++ Compiler 8.1 for Linux. Microsoft Visual C++ Toolkit 2003. To run the Live CD, complete the following steps: Download the ISO-file (about 400MB) and burn it on a CD. If you want to use the Intel C Compiler, you will need a license file. You can obtain a free non-commercial license by subscribing here. If you store the license file on a memory stick, the Live CD will recognize it automatically. Boot the CD and choose your language, keyboard layout, etc. When the screen shown in comes up, double-click on the ECRYPT test suite icon. This will install the testing framework in ~/ecrypt-test-suite, fetch updates from the eSTREAM server if requested, and immediately launch the testing process (see ). The tests can be aborted at any time by pressing Ctrl C. The Live CD does not store anything on the hard disk. Any changes you make will be lost after reboot, unless you copy them manually (e.g., on a memory stick).

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The testing framework should install and run without problems on any recent Linux distribution. Here are the Installation instructions: Download and untar the tarball of the testing framework: $ $ Correct the permissions of the scripts (this fix is necessary because the current version of ViewCVS does not understand the svn:executable property). $ $ Make sure you have a compiler (GCC) installed and configure the framework as explained in .

The shell and system utilities required by the testing framework are not present on a standard Windows platform. Fortunately, there exist several freely available software packages which provide this functionality. The instructions below explain how to install the framework using the MinGW/MSYS packages. First install an ANSI C compiler. The testing framework currently detects two compilers under Windows: Microsoft C/C++ Optimizing Compiler, which is included in Microsoft Visual Studio and can be downloaded separately from MSDN. GCC, which has been ported to Windows by the MinGW project (amongst others). The installation program is available here. Install the MSYS shell. The current version can be downloaded here. If you plan to use the MinGW compiler, make sure to install it before installing MSYS. Download the tarball of the testing framework and store it in your MSYS home directory. In a default installation, this directory is located in C:\msys\1.0\home\%USERNAME%. Open an MSYS terminal and extract the tarball: $ $ Configure the framework as explained in . If the configuration script does not detect the Microsoft Compiler, this probably indicates that the environment variables PATH, INCLUDE, and LIB are not set correctly. The correct values can be found in a file named vcvars32.bat. You can either add these variables to your system in Control Panel System Advanced Environment Variables , or (for a default installation) add the following line in C:\msys\1.0\msys.bat: C:\Program Files\Microsoft Visual C++ Toolkit 2003\vcvars32.bat

The installation instructions for UNIX platforms are the same as the ones given in . However, depending on your operating system, some of the scripts might fail to run correctly because of small compatibility problems. The easiest way to avoid this is to replace some of the UNIX utilities by their GNU equivalents: GNU Bash GNU Make GNU Coreutils With these tools installed, the framework is known to run correctly on the following platforms: HP-UX 11.00 (PA-RISC version) with HP C/HP-UX Version B.11.11.02 and/or GCC. Solaris 8 (SPARC edition) with SUN Forte Developer 7 C 5.4 and/or GCC. Tru64 UNIX V5.1B (Alpha) with Compaq C V6.5-011 and/or GCC.

It is probably not too hard to make the framework run on other systems (e.g., Mac OS X on PowerPC). As soon as we have a chance to test it, we will update this document.

This section explains how to use the scripts inluded in the testing framework. The three most important scripts are called configure, run, and collect and are located in the directory ./scripts. A fourth script, called start, runs the three previous commands one after another. In order to avoid having to prefix all commands with ./scripts/, add the scripts directory to the PATH variable: $

The configure script searches the path for compilers, tests which compiler options are supported, and collects information about the CPU. All information is stored in the directory ./reports-$HOSTNAME. The first part of the script's output is reproduced below: $ y If the list of executables above contains programs which you definitely do not want the script to run and test, simply press n, edit the file ./reports-$HOSTNAME/candidates, and start the script again. The final list of supported compilers and options is stored in ./reports-$HOSTNAME/compilers. Note that this first stage is normally only executed when the script is launched for the very first time. The script will only perform a new search, if the file ./reports-$HOSTNAME/compilers has been deleted. The second part of the script provides the possibility to enable or disable any compiler previously detected. The set of active compilers can be modified at any time by running configure again. to select everything: ]]>1,2,3 The result of the script is a list of configuration files in ./reports-$HOSTNAME/configs, each of which defines a compiler and a combination of flags. Which configurations will eventually be used during the benchmarking, and in which order, is determined by the file ./reports-$HOSTNAME/shortlist, constructed in the next step of the script: 5 y If you want the script to finish immediately after all configurations in the shortlist have been tested, answer n. The framework's default behavior is to start testing compiler options which are not on the list, until the script is either interrupted by the user (pressing Ctrl C), or all configuration files in ./reports-$HOSTNAME/configs have been tested. The last task of the configuration script is to determine the CPU's clock frequency. The correct frequency should automatically be detected on most platforms: if this is correct, or enter the clock speed: ]]>

The actual tests are launched with the command run. When invoked without arguments, the script will run through all implementations in the test suite, compile each of them using the current compiler settings, and perform the tests described in . This is repeated for all compiler configurations in ./reports-$HOSTNAME/configs (or at least those in the shortlist), and the results are stored in the current working directory. The following example shows how run is invoked in the start script (all test reports are stored in ./reports-$HOSTNAME in this case): $ $ An optional argument can be used to specify the directory which contains the implementations to be tested. If the specified path does not point to an existing directory, the script will check whether it matches a directory in submissions or benchmarks. The command below, for example, will only test the implementation of SNOW 2.0 (assuming that the scripts directory is in the PATH): $ $ $ On some platforms, the testing framework might uses the standard clock() function to measure timings. Unfortunately, this function has a rather low resolution on most platforms. As a consequence, tests need to be run for several seconds in order for the timing results to be accurate. Depending on the number of primitives and compiler options, the benchmarking can therefore take a very long time. The tests can be aborted at any time by pressing Ctrl C, though.

Once the tests are finished (or have been aborted by the user), the results can be collected with the collect command. This script traverses the current working directory tree and creates an HTML report (named index.html) summarizing the benchmark results for each subdirectory it encounters. For examples of the HTML output, see .

This section is a step-by-step guide to writing code which can easily be integrated into the testing framework. Please make sure to follow the steps described below before submitting optimized code to the eSTREAM project.

First, dowload, install, and configure the testing framework as explained in detail in and .

The easiest way to create a new API-compliant implementation of a stream cipher is to copy and edit the reference implementation included in the testing framework: $ $ $ There are a number of issues that should be taken into account when editing the source code: The optimized code should compile under any ANSI C compiler and run on any platform. This does not mean that compiler or platform specific extensions cannot be used. However, if non-standard constructs are used, then the code should first check if the extensions are supported by the compiler, and if not, provide (possibly non-optimized) alternatives. Here is an example: = 1300) /* optimized code using Microsoft Visual C++ .NET extensions */ #elif defined(__x86_64__) /* code optimized for the AMD64 architecture */ #else /* standard C code */ #endif]]> The code should also anticipate possible endianness and data alignment problems when running on non-x86 platforms. This involves the following measures: Use the UXTOY_LITTLE or UXTOY_BIG macros defined in &ecrypt-portable.h; anywhere words are stored into bytes or the other way around. These macros will change the order of the bytes on all platforms where it is required. Align all memory accesses. Several UNIX machines will generate bus errors when words loaded from or stored into the memory are not aligned on multiples of the word size. Note that the code can safely assume that all byte strings passed to the API are aligned on multiples of the largest word size supported on the machine (e.g., 128 bit on modern Pentium 4 processors). Avoid writing unnecessary complex code, i.e.: Only implement the functions strictly required by the API. Code providing additional debugging functionality, interactive user interfaces, etc. should be disabled (using #ifndef ECRYPT_API), or better yet, completely removed. Remove unused variables and 'dead' code. Manually unroll loops only if this makes the code significantly faster. An efficient C implementation, compiled with a modern compiler and with the proper optimization flags, is often pretty difficult to beat using hand-coded assembly. However, if you feel that your implementation could significantly benefit from assembly, then here are some guidelines: Always analyze the machine code generated by your C compiler before writing your own assembly. If the only purpose of the assembly is to take advantage of SIMD instructions, consider to replace it by C intrinsics (the MMX intrinsics defined in mmintrin.h, for example, are supported by GNU, Intel, and Microsoft). Avoid the use of assembly in non-critical parts of your implementation. The preferred approach is to use only a few short blocks of inline assembly in the inner loops of your algorithm. As before, make sure that the code checks whether the compiler supports the assembly syntax, for example: > 27)) + c; #endif]]> While eSTREAM does not encourage this, plain assembly implementations can also be submitted, provided that they can be processed by GCC (i.e., .s or .S files). Here is an example of a .S file:

Before submitting an optimized implementation, you should make sure that (1) it interacts correctly with the testing framework, and (2) it is indeed more efficient than the existing code. In order to verify these conditions, create a test directory and run the tests as described in : $ $ $ $ The scripts should not return any error. If they do, then the code is probably not API compliant. The sections below describe a number of common problems and explain how to resolve them.

If the compilation fails, check the error messages in errors_*. Typical compilation errors are: undefined reference to `ECRYPT_init' This message indicates that your code does not define the ECRYPT_init function. This function should always be defined, even if it is left empty. syntax error before '/' token Replace non-standard // comments by /* ... */. syntax error before "u64" On 32-bit platforms, u64 variables are defined as unsigned long long. This type exists in the ISO C99 standard, but not in ISO C89. Therefore, if your code uses u64 variables, replace the third line of the Makefile by:

If the script refuses to generate test vectors, this typically indicates that the code did not pass the API compliance tests described in . The file errors_* reports which tests failed. In order to correct these problems, make sure that: all variables that need to be transferred from one function call to another are stored in the ECRYPT_ctx structure, and not in static variables or dynamically allocated memory; all variables are initialized; the function ECRYPT_ivsetup reinitializes all variables whose values were changed during the encryption with previous IVs. Another common problem which causes the execution to fail on 64-bit machines are bus errors due to misaligned data. When loading or storing words into the memory, always make sure that they are aligned on multiples of the word size (see also ).

If the test vectors generated by the scripts differ from the ones included in the testing framework, this might have two causes: There is a bug in the optimized implementation. A common problem on UNIX platforms are endianness issues. As explained in , always use the UXTOY_LITTLE or UXTOY_BIG macros when translating bytes into words or vice versa. There was a bug in the original reference code. In this case new test vectors need to be generated. This can be done by issuing the following command in the source directory: $ If you do not have GCC installed, you will also need to specify which configuration file (see ) to use, for example: . The command above will generate a file called unverified.test-vectors, which can be renamed to verified.test-vectors once the correctness of the test vectors have been verified: $

Optimized implementations which pass all tests described above should be mailed to estreamtesting@ecrypt.eu.org. The mail should contain the following information: A .tar.gz or .zip attachment containing the following files (and only these files): an API compliant header file (i.e., the ecrypt-sync.h or ecrypt-sync-ae.h file); the .c file (and .h files, if any) implementing the primitive; a Makefile (this file should normally not have been modified); a file called verified.test-vectors containing the correct test vectors (only if the existing test vectors happened to be incorrect). A confirmation that the test vectors included in the testing framework have been verified. A note stating whether or not the implementation should replace the existing reference code.

The table below links to the most recent reports produced by the eSTREAM testing framework. These reports will regularly be updated as new implementations are submitted. It is important to emphasize that the current results are very preliminary: the implementations currently included in the framework only serve as reference code, and are not necessarily optimized. CPU Clock Model Latest reports Intel Pentium M 1700MHz 6/9/5 [revision 115] Intel Pentium 4 2.40GHz 15/2/9 [revision 115] AMD Athlon 64 3000+ 1.80GHz 15/47/0 [revision 115] Alpha EV5.6 400MHz 21164A [revision 115] HP 9000/785 875MHz J6750 [revision 115] UltraSPARC-III 750MHz V9 [revision 115]

Send your questions to estreamtesting@ecrypt.eu.org. Frequently asked questions will be added to this section.

For further information about the eSTREAM project, please visit the eSTREAM webpage and the discussion forum.

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