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Make Salsa20 variable-round, allowing for Salsa20/12 to be used for Packet encrypt and decrypt. Profiling analysis found that Salsa20 encrypt was accounting for a nontrivial percentage of CPU time, so it makes sense to cut this load fundamentally. There are no published attacks against Salsa20/12, and DJB believes 20 rounds to be overkill. This should be more than enough for our needs. Obviously incorporating ASM Salsa20 is among the next steps for performance.

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This commit is contained in:
Adam Ierymenko 2013-10-18 17:39:48 -04:00
parent 37e3bc3467
commit 8c9b73f67b
7 changed files with 41 additions and 14 deletions
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11
node/Salsa20.hpp
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@ -14,7 +14,7 @@
namespace ZeroTier {
/**
* Salsa20/20 stream cipher
* Salsa20 stream cipher
*/
class Salsa20
{
@ -25,11 +25,12 @@ public:
* @param key Key bits
* @param kbits Number of key bits: 128 or 256 (recommended)
* @param iv 64-bit initialization vector
* @param rounds Number of rounds: 8, 12, or 20
*/
Salsa20(const void *key,unsigned int kbits,const void *iv)
Salsa20(const void *key,unsigned int kbits,const void *iv,unsigned int rounds)
throw()
{
init(key,kbits,iv);
init(key,kbits,iv,rounds);
}
/**
@ -38,8 +39,9 @@ public:
* @param key Key bits
* @param kbits Number of key bits: 128 or 256 (recommended)
* @param iv 64-bit initialization vector
* @param rounds Number of rounds: 8, 12, or 20
*/
void init(const void *key,unsigned int kbits,const void *iv)
void init(const void *key,unsigned int kbits,const void *iv,unsigned int rounds)
throw();
/**
@ -67,6 +69,7 @@ public:
private:
uint32_t _state[16];
unsigned int _roundsDiv2;
};
} // namespace ZeroTier