diff options
Diffstat (limited to 'rsa/fastrsa.py')
| -rw-r--r-- | rsa/fastrsa.py | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/rsa/fastrsa.py b/rsa/fastrsa.py index 1437da7..3a26437 100644 --- a/rsa/fastrsa.py +++ b/rsa/fastrsa.py @@ -171,16 +171,16 @@ def fast_exponentiation(a, e, n): """Calculates r = a^e mod n """ #Single loop version is faster and uses less memory - #MSB is always 1 so skip testing it and start with result = a + #MSB is always 1 so skip testing it and start with next exponent bit. msbe = bit_size(e) - 2 #Find MSB-1 of exponent test = long(1 << msbe) #Isolate each exponent bit with test value a %= n #Throw away any overflow modulo n result = a #Start with result = a (skip MSB test) - while test != 0: - if e & test != 0: #If exponent bit 1 square and mult by a - result = (result * result * a) % n - else: #If exponent bit 0 just square - result = (result * result) % n + while test != 0: #Repeat til all exponent bits have been tested + if e & test != 0: #If exponent bit is 1, square and mult by a + result = (result * result * a) % n #Then reduce modulo n + else: #If exponent bit is 0, just square + result = (result * result) % n #Then reduce modulo n test >>= 1 #Move to next exponent bit return result |