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require File.expand_path(File.dirname(__FILE__) + '/util')
module SRP
class Server
include Util
def initialize(salt, verifier)
@salt = salt
@verifier = verifier
end
def initialize_auth(aa)
@aa = aa
@b = bigrand(32).hex
# B = g^b + k v (mod N)
@bb = (modpow(GENERATOR, @b, PRIME_N) + multiplier * @verifier) % PRIME_N
u = calculate_u(@aa, @bb, PRIME_N)
return @bb, u
end
def authenticate(m)
u = calculate_u(@aa, @bb, PRIME_N)
base = (modpow(@verifier, u, PRIME_N) * @aa) % PRIME_N
server_s = modpow(base, @b, PRIME_N)
if(m == calculate_m(@aa, @bb, server_s))
return calculate_m(@aa, m, server_s)
end
end
protected
def calculate_u(aa, bb, n)
nlen = 2 * ((('%x' % [n]).length * 4 + 7) >> 3)
aahex = '%x' % [aa]
bbhex = '%x' % [bb]
return sha256_str("%x%x" % [aa, bb]).hex
hashin = '0' * (nlen - aahex.length) + aahex \
+ '0' * (nlen - bbhex.length) + bbhex
sha256_str(hashin).hex
end
end
end
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