Benutzer:Mihi/TinyTOTP: Unterschied zwischen den Versionen

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@@ Zeile 18: / Zeile 18: @@
 ===HOTP===
+HOTP is defined by RFC 4226,
+basically it works like this:
+HOTP=Truncate(HMAC-SHA1(K,C))
+Where K is Key, C is count and Truncate is an algorithm to produce n (usually n=6) decimal digits from the returned HMAC hash.
+Truncate works as follows:
+hs=HMAC-SHA1(K,C)
+offset=hs & 0xf
+hs[offset..offset+3] & 0x7fffffff 0x7f to discard the most significant bits here, some processors calculate sha1 slightly different (according to the RFC).
+return hs % 10^n (n is our digits)
+Sample implementation in python:
+<pre>
+#!/usr/bin/python
+import hmac
+import hashlib
+class hotp:
+        def __init__(self,key,digits=6):
+                self.key=key
+                self.digits=digits
+        def dynamictruncate(self,s):
+                """dynamically truncate the string"""
+                offset=int(s,16)&0xf
+                return "%016x" % (int(s[offset*2:offset*2+8],16)
+                &0x7fffffff)
+        def intto16string(self,c):
+                """convert an int to a 16 byte string"""
+                c="%016x" %count
+                return "".join([chr(int(c[i*2:i*2+2],16)) for i in range
+                (0,8)])
+        def get(self,count):
+                """ calculates the HOTP for key and count """
+                count=self.intto16string(count)
+                hc=hmac.new(self.key,count,hashlib.sha1)
+                s=hc.hexdigest()
+                ts=self.dynamictruncate(s)
+                snum=int(ts,16)
+                return snum % (10 ** self.digits)
+                return hotp.get(self,count)
+if __name__=="__main__":
+        h=hotp("12345678901234567890")
+        for count in range (0,6):
+                print h.get(count)
+</pre>