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-rw-r--r--lib/srp/server.rb42
1 files changed, 42 insertions, 0 deletions
diff --git a/lib/srp/server.rb b/lib/srp/server.rb
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--- /dev/null
+++ b/lib/srp/server.rb
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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)
+ @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(aa, client_s)
+ u = calculate_u(aa, @bb, PRIME_N)
+ base = (modpow(@verifier, u, PRIME_N) * aa) % PRIME_N
+ server_s = modpow(base, @b, PRIME_N)
+ return client_s == server_s
+ end
+
+
+ protected
+
+ def calculate_u(aa, bb, n)
+ nlen = 2 * ((('%x' % [n]).length * 4 + 7) >> 3)
+ aahex = '%x' % [aa]
+ bbhex = '%x' % [bb]
+ hashin = '0' * (nlen - aahex.length) + aahex \
+ + '0' * (nlen - bbhex.length) + bbhex
+ sha1_hex(hashin).hex
+ end
+ end
+end
+
+