A cryptographic system for reproducibly establishing a cryptographic key comprising - a physical system comprising a physical, at least partially random, configuration of components, - an initial bit-string producer for establishing an initial bit-string, the initial bit-string depending on the configuration, - a normalizer for establishing in dependency on the initial-bit string a first correctable bit-string, the first correctable bit-string lying in a correctable neighborhood of an error correcting code, a pre-determined error correcting algorithm for mapping an element of the correctable neighborhood to a code word being associated with the error correcting code, - an error-corrector, for establishing a first code word of an error correcting code in dependency on the first correctable bit-string using the error correcting algorithm, - a key establisher for establishing the cryptographic key in dependency on the first code word by applying a pre-determined key derivation algorithm, characterized in that - the cryptographic system further comprises a code word adder, a code word subtractor, and a randomizer for producing a randomizing component, the randomizing component comprises a random code word of the error correcting code, - the establishing of the first correctable bit-string is further dependent on the randomizing component, the normalizer being coupled to the code word adder for adding at least the random code word to at least the initial bit-string, - the establishing of the cryptographic key is further dependent on the randomizing component for making the cryptographic key reproducible by removing the effect of the randomizing component, the key establisher being coupled to the code word subtractor for subtracting the random code word from the first code word. - a physical system comprising a physical, at least partially random, configuration of components, - an initial bit-string producer for establishing an initial bit-string, the initial bit-string depending on the configuration, - a normalizer for establishing in dependency on the initial-bit string a first correctable bit-string, the first correctable bit-string lying in a correctable neighborhood of an error correcting code, a pre-determined error correcting algorithm for mapping an element of the correctable neighborhood to a code word being associated with the error correcting code, - an error-corrector, for establishing a first code word of an error correcting code in dependency on the first correctable bit-string using the error correcting algorithm, - a key establisher for establishing the cryptographic key in dependency on the first code word by applying a pre-determined key derivation algorithm, characterized in that - the cryptographic system further comprises a code word adder, a code word subtractor, and a randomizer for producing a randomizing component, the randomizing component comprises a random code word of the error correcting code, - the establishing of the first correctable bit-string is further dependent on the randomizing component, the normalizer being coupled to the code word adder for adding at least the random code word to at least the initial bit-string, - the establishing of the cryptographic key is further dependent on the randomizing component for making the cryptographic key reproducible by removing the effect of the randomizing component, the key establisher being coupled to the code word subtractor for subtracting the random code word from the first code word.