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Diffstat (limited to 'src/lib/crypto/builtin/aes/aes.txt')
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1 files changed, 607 insertions, 55 deletions
diff --git a/src/lib/crypto/builtin/aes/aes.txt b/src/lib/crypto/builtin/aes/aes.txt index b644b5e..25710f2 100644 --- a/src/lib/crypto/builtin/aes/aes.txt +++ b/src/lib/crypto/builtin/aes/aes.txt @@ -1,70 +1,622 @@ An AES (Rijndael) Implementation in C/C++ (as specified in FIPS-197) --------------------------------------------------------------------- - -The source code files are as follows: - -1. aes.h: the header file required to use AES in C -2. aescpp.h the header file required to use AES in C++ -3. aescrypt.c the main C source code file for encryption and decryption -4. aeskey.c the main C source code file for the key schedule -5. aestab.c the main file for the AES tables -6. aesopt.h the file for common code and for setting build options -7. aescrypt.asm a faster alternative to 3 above in assembler (using NASM) -8. uitypes.h a file for defining fixed length unsigned integer types -9. aescrypp.c an alternative to 3 for all Rijndael block and key sizes -10.aeskeypp.c an alternative to 4 for all Rijndael block and key sizes -11.aesxam.c an example of AES use - -Source files 9 and 10 are much slower than 4 and 5 for normal use and -should not be used unless support for 20 and 28 byte blocks and keys -is necessary. Files 4 and 5 provide support for block and key sizes -of 16, 24 and 32 bytes (fixed or variable) but the assemler code in -file 7 only supports the 16 byte AES block length. It does, however, -offer the three key sizes when used with file 4. The use of files 4 -and 5 (or 9 and 10) with variable block size should be avoided since -the code is much faster when the block size is fixed. - -The VC++ AES Development Project --------------------------------- - -The VC++ SOlution contains the following sub-projects - -1. aes_asm this project tests the assembler code implementation -2. aes_dll this project builds the DLL version -3. aes_gav this project re-creates the test vector files and - optionally checks them against a reference set -4. aes_rav this project checks the values produced by the code - against the values in the test vector files -5. aes_tmr this project measures the speed of the code -6. aes_tst this project is set up to test the extended version - of Rijndael with block and key sizes of 16, 20, 24, - 28 and 32 bytes -7. aes_xam this project builds the example of AES use in a - simple file encryption program - -Note that the paths for the various directories have to be set up in -aestst.h - -The AES and Rijndael Test Vector Files --------------------------------------- +==================================================================== + +Change (26/09/2018) +=================== + +1. Changes to test programs to allow them to be built on Linux/GCC + (with thanks to Michael Mohr). + +2. Rationalisation of the defines DLL_IMPORT, DYNAMIC_DLL and USE_DLL + in the test code - now DLL_IMPORT and DLL_DYNAMIC_LOAD + +3. Update the test_avs test to allow the testing of static, DLL and + dynamically loaded DLL libraries. + +Change (21/05/2018) +=================== + +1. Properly dectect presence of AESNI when using GCC (my thanks to + Peter Gutmann for this fix) + +Changes (6/12/2016) +==================== + +1. Changed function definition of has_aes_ni() to has_aes_ni(void), + suggested by Peter Gutmann + +2. Changed the default location for the vsyasm assembler to: + C:\Program Files\yasm + +Changes (27/09/2015) +==================== + +1. Added automatic dynamic table initialisation (my thanks to + Henrik S. Gaßmann who proposed this addition). + +Changes (09/09/2014) +==================== + +1. Added the ability to use Intel's hardware support for AES + with GCC on Windows and Linux + +Changes (01/09/2014) +==================== + +1. Clarify some user choices in the file aes_amd64.asm + +2. Change the detection of the x86 and x86_64 processors + in aesopt.h to allow assembler code use with GCC + +Changes (14/11/2013) +==================== + +1. Added the ability to use Intel's hardware support for AES + on Windows using Microsoft Visual Studio. + +2. Added the include 'stdint.h' and used the uint<xx>_t instead + of the old uint_<xx>t (e.g. uint_32t is now uint32_t). + +3. Added a missing .text directive in aes_x86_v2.asm that caused + runtime errors in one build configuration. + +Changes (16/04/2007) +==================== + +These changes remove errors in the VC++ build files and add some +improvements in file naming consitency and portability. There are +no changes to overcome reported bugs in the code. + +1. gen_tabs() has been renamed to aes_init() to better decribe its + function to those not familiar with AES internals. + +2. via_ace.h has been renamed to aes_via_ace.h. + +3. Minor changes have been made to aestab.h and aestab.c to enable + all the code to be compiled in either C or C++. + +4. The code for detecting memory alignment in aesmdoes.c has been + simplified and a new routine has been added: + + aes_test_alignment_detection() + + to check that the aligment test is likely to be correct. + +5. The addition of support for Structured Exception Handling (SEH) + to YASM (well done Peter and Michael!) has allowed the AMD64 + x64 assembler code to be changed to comply with SEH requriements. + +6. Corrections to build files (for win32 debug build). + +Overview +======== + +This code implements AES for both 32 and 64 bit systems with optional +assembler support for x86 and AMD64/EM64T (but optimised for AMD64). + +The basic AES source code files are as follows: + +aes.h the header file needed to use AES in C +aescpp.h the header file required with to use AES in C++ +aesopt.h the header file for setting options (and some common code) +aestab.h the header file for the AES table declaration +aescrypt.c the main C source code file for encryption and decryption +aeskey.c the main C source code file for the key schedule +aestab.c the main file for the AES tables +brg_types.h a header defining some standard types and DLL defines +brg_endian.h a header containing code to detect or define endianness +aes_x86_v1.asm x86 assembler (YASM) alternative to aescrypt.c using + large tables +aes_x86_v2.asm x86 assembler (YASM) alternative to aescrypt.c using + compressed tables +aes_amd64.asm AMD64 assembler (YASM) alternative to aescrypt.c using + compressed tables + +In addition AES modes are implemented in the files: + +aes_modes.c AES modes with optional support for VIA ACE detection and use +aes_via_ace.h the header file for VIA ACE support + +and Intel hardware support for AES (AES_NI) is implemented in the files + +aes_ni.h defines for AES_NI implementation +aes_ni.c the AES_NI implementation + +Other associated files for testing and support are: + +aesaux.h header for auxilliary routines for testsing +aesaux.c auxilliary routines for testsingt +aestst.h header file for setting the testing environment +rdtsc.h a header file that provides access to the Time Stamp Counter +aestst.c a simple test program for quick tests of the AES code +aesgav.c a program to generate and verify the test vector files +aesrav.c a program to verify output against the test vector files +aestmr.c a program to time the code on x86 systems +modetest.c a program to test the AES modes support +vbxam.doc a demonstration of AES DLL use from Visual Basic in Microsoft Word +vb.txt Visual Basic code from the above example (win32 only) +aesxam.c an example of AES use +tablegen.c a program to generate a simplified 'aestab.c' file for + use with compilers that find aestab.c too complex +yasm.rules the YASM build rules file for Microsoft Visual Studio 2005 +via_ace.txt describes support for the VIA ACE cryptography engine +aes.txt this file + +Building The AES Libraries +-------------------------- + +A. Versions +----------- + +The code can be used to build static and dynamic libraries, each in five +versions: + + Key scheduling code in C, encrypt/decrypt in: + + C C source code (win32 and x64) + ASM_X86_V1C large table x86 assembler code (win32) + ASM_X86_V2C compressed table x86 assembler code (win32) + ASM_AMD64 compressed table x64 assembler code (x64) + + Key scheduling and encrypt/decrypt code in assembler: + + ASM_X86_V2 compressed table x86 assembler (win32) + +The C version can be compiled for Win32 or x64 whereas the x86 and x64 +assembler versions are for Win32 and x64 respectively. + +If Intel's hardware support for AES (AES_NI) is available, it can be used +with either the C or the ASM_AMD64 version. If ASM_AMD64 is to be used, it +is important that the define USE_INTEL_AES_IF_PRESENT in asm_amd64.asm is +set to the same value as it has in aesopt.h + +B. YASM +------- + +If you wish to use the x86 assembler files you will also need the YASM open +source x86 assembler (r1331 or later) for Windows which can be obtained from: + + http://www.tortall.net/projects/yasm/ + +This assembler (vsyasm.exe) should be placed in the directory: + + C:\Program Files\yasm + +C. Configuration +---------------- + +The following configurations are available as projects for Visual Studio +but the following descriptions should allow them to be built in other x86 +environments + + lib_generic_c Win32 and x64 + headers: aes.h, aesopt.h, aestab.h, brg_endian.h, tdefs.h + (+ aes_ni.h for AES_NI) + C source: aescrypt.c, aeskey.c, aestab.c, aes_modes.c + (+ aes_ni.c for AES_NI) + defines + + dll_generic_c Win32 and x64 + headers: aes.h, aesopt.h, aestab.h, brg_endian.h, tdefs.h + (+ aes_ni.h for AES_NI) + C source: aescrypt.c, aeskey.c, aestab.c, aes_modes.c + (+ aes_ni.c for AES_NI) + defines DLL_EXPORT + + lib_asm_x86_v1c Win32 + headers: aes.h, aesopt.h, aestab.h, brg_endian.h, tdefs.h + C source: aeskey.c, aestab.c, aes_modes.c + x86 assembler: aes_x86_v1.asm + defines ASM_X86_V1C (set for C and assembler files) + + dll_asm_x86_v1c Win32 + headers: aes.h, aesopt.h, aestab.h, brg_endian.h, tdefs.h + C source: aeskey.c, aestab.c, aes_modes.c + x86 assembler: aes_x86_v1.asm + defines DLL_EXPORT, ASM_X86_V1C (set for C and assembler files) + + lib_asm_x86_v2c Win32 + headers: aes.h, aesopt.h, aestab.h, brg_endian.h, tdefs.h + C source: aeskey.c, aestab.c, aes_modes.c + x86 assembler: aes_x86_v2.asm + defines ASM_X86_V2C (set for C and assembler files) + + dll_asm_x86_v2c Win32 + headers: aes.h, aesopt.h, aestab.h, brg_endian.h, tdefs.h + C source: aeskey.c, aestab.c, aes_modes.c + x86 assembler: aes_x86_v1.asm + defines DLL_EXPORT, ASM_X86_V2C (set for C and assembler files) + + lib_asm_x86_v2 Win32 + headers: aes.h, aesopt.h, aestab.h, brg_endian.h, tdefs.h + C source: aes_modes.c + x86 assembler: aes_x86_v1.asm + defines ASM_X86_V2 (set for C and assembler files) + + dll_asm_x86_v2 Win32 + headers: aes.h, aesopt.h, aestab.h, brg_endian.h, tdefs.h + C source: aes_modes.c + x86 assembler: aes_x86_v1.asm + defines DLL_EXPORT, ASM_AMD64_C (set for C and assembler files) + + lib_asm_amd64_c x64 + headers: aes.h, aesopt.h, aestab.h, brg_endian.h, tdefs.h + (+ aes_ni.h for AES_NI) + C source: aes_modes.c (+ aes_ni.c for AES_NI) + x86 assembler: aes_amd64.asm + defines ASM_AMD64_C (set for C and assembler files) + + dll_asm_amd64_c x64 + headers: aes.h, aesopt.h, aestab.h, brg_endian.h, tdefs.h + (+ aes_ni.h for AES_NI) + C source: aes_modes.c (+ aes_ni.c for AES_NI) + x86 assembler: aes_amd64.asm + defines DLL_EXPORT, ASM_AMD64_C (set for C and assembler files) + +Notes: + +ASM_X86_V1C is defined if using the version 1 assembler code (aescrypt1.asm). + The defines in the assember file must match those in aes.h and + aesopt.h). Also remember to include/exclude the right assembler + and C files in the build to avoid undefined or multiply defined + symbols - include aes_x86_v1.asm and exclude aescrypt.c + +ASM_X86_V2 is defined if using the version 2 assembler code (aes_x86_v2.asm). + This version provides a full, self contained assembler version + and does not use any C source code files except for the mutiple + block encryption modes that are provided by aes_modes.c. The define + ASM_X86_V2 must be set on the YASM command line (or in aes_x86_v2.asm) + to use this version and all C files except aec_modes.c and, for the + DLL build, aestab.c must be excluded from the build. + +ASM_X86_V2C is defined when using the version 2 assembler code (aes_x86_v2.asm) + with faster key scheduling provided by the in C code (the options in + the assember file must match those in aes.h and aesopt.h). In this + case aeskey.c and aestab.c are needed with aes_x86_v2.asm and the + define ASM_X86_V2C must be set for both the C files and for + aes_x86_v2.asm in the build commands(or in aesopt.h and aes_x86_v2.asm). + Include aes_x86_v2.asm, aeskey.c and aestab.c, exclude aescrypt.c for + this option. + +ASM_AMD64_C is defined when using the AMD64 assembly code because the C key + scheduling is used in this case. + +DLL_EXPORT must be defined to generate the DLL version of the code and + to run tests on it + +DLL_IMPORT must be defined to use the DLL version of the code in an + application program + +Directories the paths for the various directories for test vector input and + output have to be set in aestst.h + +VIA ACE see the via_ace.txt for this item + +Static The static libraries are named: +Libraries + aes_lib_generic_c.lib + aes_lib_asm_x86_v1c.lib + aes_lib_asm_x86_v2.lib + aes_lib_asm_x86_v2c.lib + aes_lib_asm_amd64_c.lib + + and placed in one of the the directories: + + lib\win32\release\ + lib\win32\debug\ + lib\x64\release\ + lib\x64\debug\ + + in the aes root directory depending on the platform(win32 or + x64) and the build (release or debug). After any of these is + built it is then copied into the aes\lib directory, which is + the library location that is subsequently used for testing. + Hence testing is always for the last static library built. + +Dynamic These libraries are named: +Libraries + aes_lib_generic_c.dll + aes_lib_asm_x86_v1c.dll + aes_lib_asm_x86_v2.dll + aes_lib_asm_x86_v2c.dll + aes_lib_asm_amd64_c.dll + + and placed in one of the the directories: + + dll\win32\release\ + dll\win32\debug\ + dll\x64\release\ + dll\x64\debug\ + + in the aes root directory depending on the platform(win32 or + x64) and the build (release or debug). Each DLL library: + + aes_<ext>.dll + + has three associated files: + + aes_dll_<ext>.lib the library file for implicit linking + aes_dll_<ext>.exp the exports file + aes_dll_<ext>.pdb the symbol file + + After any DLL is built it and its three related files are then + copied to the aes\dll directory, which is the library location + used in subsequent testing. Hence testing is always for the + last DLL built. + +D. Testing +---------- + +These tests require that the test vector files are placed in the 'testvals' +subdirectory. If the AES Algorithm Validation Suite tests are used then +the *.fax files need to be put in the 'testvals\fax' subdirectory. This is +covered in more detail below. + +The projects test_lib and time_lib are used to test and time the last static +library built. They use the files: + + test_lib: Win32 (x64 for the C and AMD64 versions) + headers: aes.h, aescpp.h, brg_types.h, aesaux.h and aestst.h + C source: aesaux.c, aesrav.c + defines: + + time_lib: Win32 (x64 for the C and AMD64 versions) + headers: aes.h, aescpp.h, brg_types.h, aesaux.h, aestst.h and rdtsc.h + C source: aesaux.c, aestmr.c + defines: + +The projects test_dll and time_dll are used to test and time the last DLL +built. These use the files: + + test_dll: Win32 (x64 for the C and AMD64 versions) + headers: aes.h, aescpp.h, brg_types.h, aesaux.h and aestst.h + C source: aesaux.c, aesrav.c + defines: DLL_IMPORT + + time_dll: Win32 (x64 for the C and AMD64 versions) + headers: aes.h, aescpp.h, brg_types.h, aesaux.h aestst.h and rdtsc.h + C source: aesaux.c, aestmr.c + defines: DLL_IMPORT + +and default to linkingto with the AES DLL using dynamic (run-time) linking. Implicit +linking can be used by adding the lib file associated with the AES DLL (in the aes\dll +sub-directory) to the build (under project Properties|Linker in Visual Studio) and +removing the DLL_DYNAMIC_LOAD define (under project Properties|C/C++|Preprocessor). + +0 Link is linked into this project and the symbol +DLL_DYNAMIC_LOAD is left undefined, then implicit linking will be used + +The above tests take command line arguments that determine which test are run +as follows: + + test_lib /t:[knec] /k:[468] + test_dll /t:[knec] /k:[468] + +where the symbols in square brackets can be used in any combination (without +the brackets) and have the following meanings: + + /t:[knec] selects which tests are used + /k:[468] selects the key lengths used + /c compares output with reference (see later) + + k: generate ECB Known Answer Test files + n: generate ECB Known Answer Test files (new) + e: generate ECB Monte Carlo Test files + c: generate CBC Monte Carlo Test files + +and the characters giving the lengths are digits representing the key lengths +in 32-bit units (4, 6, 8 for lengths of 128, 192 or 256 bits respectively). + +The project test_modes tests the AES modes. It uses the files: + + test_modes: Win32 or x64 + headers: aes.h, aescpp.h, brg_types.h, aesaux,h and aestst.h + C source: aesaux.c, modetest.c + defines: none for static library test, DLL_IMPORT for DLL test + +which again links to the last library built. + +E. Other Applications +--------------------- + +These are: + + gen_tests builds the test_vector files. The commad line is + gen_tests /t:knec /k:468 /c + as described earlier + + test_aes_avs run the AES Algorithm Validation Suite tests for + ECB, CBC, CFB and OFB modes + + gen_tables builds a simple version of aes_tab.c (in aestab2.c) + for compilers that cannot handle the normal version + aes_example provides an example of AES use + +These applications are linked to the last static library built or, if +DLL_IMPORT is defined during compilation, to the last DLL built. + +F. Use of the VIA ACE Cryptography Engine (x86 only) +---------------------------------------------------- + +The use of the code with the VIA ACE cryptography engine in described in the +file via_ace.txt. In outline aes_modes.c is used and USE_VIA_ACE_IF_PRESENT +is defined either in section 2 of aesopt.h or as a compilation option in Visual +Studio. If in addition ASSUME_VIA_ACE_PRESENT is also defined then all normal +AES code will be removed if not needed to support VIA ACE use. If VIA ACE +support is needed and AES assembler is being used only the ASM_X86_V1C and +ASM_X86_V2C versions should be used since ASM_X86_V2 and ASM_AMD64 do not +support the VIA ACE engine. + +G. The AES Test Vector Files +---------------------------- These files fall in the following groups (where <nn> is a two digit number): 1. ecbvk<nn>.txt ECB vectors with variable key 2. ecbvt<nn>.txt ECB vectors with variable text -3. ecbnk<nn>.txt new ECB vectors with variable key +3. ecbnk<nn>.txt new ECB vectors with variable key 4. ecbnt<nn>.txt new ECB vectors with variable text 5. ecbme<nn>.txt ECB monte carlo encryption test vectors 6. ecbmd<nn>.txt ECB monte carlo decryption test vectors 7. cbcme<nn>.txt CBC monte carlo encryption test vectors 8. cbcmd<nn>.txt CBC monte carlo decryption test vectors -The first digit of the numeric suffix on the filename gives the -block size in 32bit units and the second numeric digit gives the -key size. For example, the file ecbvk44.txt provides the test -vectors for ECB encryption with a 128 bit block size and a 128 -bit key size. +The first digit of the numeric suffix on the filename gives the block size +in 32 bit units and the second numeric digit gives the key size. For example, +the file ecbvk44.txt provides the test vectors for ECB encryption with a 128 +bit block size and a 128 bit key size. The test routines expect to find these +files in the 'testvals' subdirectory within the aes root directory. The +'outvals' subdirectory is used for outputs that are compared with the files +in 'testvals'. Note that the monte carlo test vectors are the result of +applying AES iteratively 10000 times, not just once. + +The AES Algorithm Validation Suite tests can be run for ECB, CBC, CFB and +OFB modes (CFB1 and CFB8 are not implemented). The test routine uses the +*.fax test files, which should be placed in the 'testvals\fax' subdirectory. + +H. The Basic AES Calling Interface +---------------------------------- + +The basic AES code keeps its state in a context, there being different +contexts for encryption and decryption: + + aes_encrypt_ctx + aes_decrypt_ctx + +The AES code is initialised with the call + + aes_init(void) + +although this is only essential if the option to generate the AES tables at +run-time has been set in the options (i.e.fixed tables are not being used). + +The AES encryption key is set by one of the calls: + + aes_encrypt_key128(const unsigned char *key, aes_encrypt_ctx cx[1]) + aes_encrypt_key192(const unsigned char *key, aes_encrypt_ctx cx[1]) + aes_encrypt_key256(const unsigned char *key, aes_encrypt_ctx cx[1]) + +or by: + + aes_encrypt_key(const unsigned char *key, int key_len, + aes_encrypt_ctx cx[1]) + +where the key length is set by 'key_len', which can be the length in bits +or bytes. + +Similarly, the AES decryption key is set by one of: + + aes_decrypt_key128(const unsigned char *key, aes_decrypt_ctx cx[1]) + aes_decrypt_key192(const unsigned char *key, aes_decrypt_ctx cx[1]) + aes_decrypt_key256(const unsigned char *key, aes_decrypt_ctx cx[1]) + +or by: + + aes_decrypt_key(const unsigned char *key, int key_len, + aes_decrypt_ctx cx[1]) + +Encryption and decryption for a single 16 byte block is then achieved using: + + aes_encrypt(const unsigned char *in, unsigned char *out, + const aes_encrypt_ctx cx[1]) + aes_decrypt(const unsigned char *in, unsigned char *out, + const aes_decrypt_ctx cx[1]) + +The above subroutines return a value of EXIT_SUCCESS or EXIT_FAILURE +depending on whether the operation succeeded or failed. + +I. The Calling Interface for the AES Modes +------------------------------------------ + +The subroutines for the AES modes, ECB, CBC, CFB, OFB and CTR, each process +blocks of variable length and can also be called several times to complete +single mode operations incrementally on long messages (or those messages, +not all of which are available at the same time). The calls: + + aes_ecb_encrypt(const unsigned char *ibuf, unsigned char *obuf, + int len, const aes_encrypt_ctx cx[1]) + + aes_ecb_decrypt(const unsigned char *ibuf, unsigned char *obuf, + int len, const aes_decrypt_ctx cx[1]) + +for ECB operations and those for CBC: + + aes_cbc_encrypt(const unsigned char *ibuf, unsigned char *obuf, + int len, unsigned char *iv, const aes_encrypt_ctx cx[1]) + + aes_cbc_decrypt(const unsigned char *ibuf, unsigned char *obuf, + int len, unsigned char *iv, const aes_decrypt_ctx cx[1]) + +can only process blocks whose lengths are multiples of 16 bytes but the calls +for CFB, OFB and CTR mode operations: + + aes_cfb_encrypt(const unsigned char *ibuf, unsigned char *obuf, + int len, unsigned char *iv, aes_encrypt_ctx cx[1]) + + aes_cfb_decrypt(const unsigned char *ibuf, unsigned char *obuf, + int len, unsigned char *iv, aes_encrypt_ctx cx[1]) + + aes_ofb_encrypt(const unsigned char *ibuf, unsigned char *obuf, + int len, unsigned char *iv, aes_encrypt_ctx cx[1]) + + aes_ofb_decrypt(const unsigned char *ibuf, unsigned char *obuf, + int len, unsigned char *iv, aes_encrypt_ctx cx[1]) + + aes_ctr_encrypt(const unsigned char *ibuf, unsigned char *obuf, + int len, unsigned char *cbuf, cbuf_inc ctr_inc, aes_encrypt_ctx cx[1]) + + aes_ctr_decrypt(const unsigned char *ibuf, unsigned char *obuf, + int len, unsigned char *cbuf, cbuf_inc ctr_inc, aes_encrypt_ctx cx[1]) + +can process blocks of any length. Note also that CFB, OFB and CTR mode calls only +use AES encryption contexts even during decryption operations. + +The calls CTR mode operations use a buffer (cbuf) which holds the counter value +together with a function parameter: + + void cbuf_inc(unsigned char *cbuf); + +that is ued to update the counter value after each 16 byte AES operation. The +counter buffer is updated appropriately to allow for incremental operations. + +Please note the following IMPORTANT points about the AES mode subroutines: - Brian Gladman <brg@gladman.uk.net>
\ No newline at end of file + 1. All modes are reset when a new AES key is set. + + 2. Incremental calls to the different modes cannot + be mixed. If a change of mode is needed a new + key must be set or a reset must be issued (see + below). + + 3. For modes with IVs, the IV value is an input AND + an output since it is updated after each call to + the value needed for any subsequent incremental + call(s). If the mode is reset, the IV hence has + to be set (or reset) as well. + + 4. ECB operations must be multiples of 16 bytes + but do not need to be reset for new operations. + + 5. CBC operations must also be multiples of 16 + bytes and are reset for a new operation by + setting the IV. + + 6. CFB, OFB and CTR mode must be reset by setting + a new IV value AND by calling: + + aes_mode_reset(aes_encrypt_ctx cx[1]) + + For CTR mode the cbuf value also has to be reset. + + 7. CFB, OFB and CTR modes only use AES encryption + operations and contexts and do not need AES + decryption operations. + + 8. AES keys remain valid across resets and changes + of mode (but encryption and decryption keys must + both be set if they are needed). + + Brian Gladman 26/09/2018 +
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