Decisional Diffie Hellman
- Decisional Diffie Hellman
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Das Decisional-Diffie-Hellman-Problem (kurz DDH) ist eine Variante des Diffie-Hellman-Problems, bei dem es um die Schwierigkeit geht, aus einer vorgegebenen Zahl ihre - in groben Zügen bekannte- Konstruktionsweise zu erraten. Somit ist DDH ein wichtiges Konstrukt in der Kryptographie und speziell der Public-Key-Kryptographie. Dazu verwandt sind das Computational-Diffie-Hellman-Problem (CDH) und der diskrete Logarithmus.
Definition
Beim Decisional Diffie Hellman Problem hat man ein Tripel an Zahlen aus Z / pZ und einen Generator g, der alle Elemente des Körpers Z / pZ erzeugen kann.
Dann hat man (ga,gb,c) und muss entscheiden, ob c eine Zufallszahl ist, oder gleich g(a * b). Es wird angenommen, dass dieses Problem NP-Schwer ist.
Weblinks
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