1 files changed, 43 insertions, 0 deletions
diff --git a/lib/srp/authentication.rb b/lib/srp/authentication.rb
new file mode 100644
index 0000000..1f36dd7
--- /dev/null
+++ b/lib/srp/authentication.rb
@@ -0,0 +1,43 @@
+require File.expand_path(File.dirname(__FILE__) + '/util')
+
+module SRP
+  module Authentication
+
+    include Util
+
+
+    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
+
+