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infra: explain choice of CRC-like algorithms

This commit is contained in:
Thomas Schoebel-Theuer 2022-03-03 05:56:44 +01:00
parent bde27c499c
commit c98e2757df
1 changed files with 46 additions and 2 deletions
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48
kernel/mars_generic.c
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@ -59,7 +59,7 @@ char *my_id(void)
if (unlikely(!id[0])) {
struct new_utsname *u;
//down_read(&uts_sem); // FIXME: this is currenty not EXPORTed from the kernel!
//down_read(&uts_sem); // FIXME: this is currently not EXPORTed from the kernel!
u = utsname();
if (u) {
strncpy(id, u->nodename, sizeof(id));
@ -159,10 +159,54 @@ __u32 used_net_digest = 0;
/* For now, use shash.
* Later, asynchronous support should be added for full exploitation
* of crypto hardware.
* of _parallelizing_ (!) (so-called crypto) hardware.
*/
#include <crypto/hash.h>
/* IMPORTANT:
* Currently, we prefer CRC-like digest algorithms
* in place of "true security". Do not conclude from the infix
* CRYPTO that we would talk about real security. Instead, we are
* talking (in order) about
*
* 1) _reliability_ of data in (long-distance) _distributed_ systems
* 2) performance _penalties_
*
* Over the next years / decades, better hardware support for these goals may
* evolve. Do not blindly believe that everything called "crypto" will be
* valuable for the above goals.
*
* Here is some rough estimate about _candidates_ for the timescale
* of decades:
*
* ~/linux-next.git> grep "config CRYPTO_CRC" $(find . -name "Kconf*")
* ./crypto/Kconfig:config CRYPTO_CRC32C
* ./crypto/Kconfig:config CRYPTO_CRC32C_INTEL
* ./crypto/Kconfig:config CRYPTO_CRC32C_VPMSUM
* ./crypto/Kconfig:config CRYPTO_CRC32C_SPARC64
* ./crypto/Kconfig:config CRYPTO_CRC32
* ./crypto/Kconfig:config CRYPTO_CRC32_PCLMUL
* ./crypto/Kconfig:config CRYPTO_CRC32_MIPS
* ./crypto/Kconfig:config CRYPTO_CRCT10DIF
* ./crypto/Kconfig:config CRYPTO_CRCT10DIF_PCLMUL
* ./crypto/Kconfig:config CRYPTO_CRCT10DIF_VPMSUM
* ./arch/arm64/crypto/Kconfig:config CRYPTO_CRCT10DIF_ARM64_CE
* ./arch/arm/crypto/Kconfig:config CRYPTO_CRCT10DIF_ARM_CE
* ./arch/arm/crypto/Kconfig:config CRYPTO_CRC32_ARM_CE
* ./drivers/crypto/Kconfig:config CRYPTO_CRC32_S390
*
* Please to _not_ extend the current list of digest algorithms with TONS
* of available algorithms, because somebody just "claims" that it were
* a "good" algorithm.
*
* You need to _measure_ on more or less _generic_ SERVER hardware (not on
* Raspberry PI & co) that it actually is faster by at least 30% than the
* currently best CRC32 family.
*
* Please do not bother me with any non- _generalizable_ (!) improvements
* below 30%.
*/
static struct crypto_shash *md5_tfm = NULL;
#ifdef HAS_CRC32C