Method and arrangement for the computer-aided exchange of cryptographic keys between a first computer unit and a second computer unit
First Claim
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1. A method for computer-aided interchange of cryptographic keys between a first computer unit and a second computer unit, which comprises:
- in the first computer unit, forming a first value from a first random number using a generating element of a finite group;
transmitting a first message, which at least contains the first value, from the first computer unit to the second computer unit;
in the second computer unit, forming a session key using a first hash function;
a first input variable for the first hash function including at least one first term that is formed by exponentiation of the first value using a secret network key;
in the first computer unit, forming the session key using the first hash function;
a second input variable for the first hash function including at least one second term that is formed by exponentiation of a public network key using the first random number;
in the first computer unit, forming a fourth input variable using a given hash function selected from the group consisting of the first hash function and a second hash function;
a third input variable for the given hash function including, for forming the fourth input variable, at least one variable that can be used to unambiguously infer the session key, at least part of the at least one variable being a nonpublic variable;
in the first computer unit, using a first signature function to form a signature term from at least the fourth input variable;
transmitting a third message, which at least includes the signature term, from the first computer unit to the second computer unit; and
in the second computer unit, verifying the signature term.
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Abstract
The invention relates to a method which can be used to declare a session key (K) between a first computer unit (U) and a second computer unit (N) without it being possible for an unauthorized third party to obtain useful information regarding the keys or the identity of the first computer unit (U). This is achieved by embedding the principle of El-Gamal key interchange in the method with additional formation of a digital signature using a hash value whose input variable contains at least variables which can be used to infer the session key unambiguously.
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Citations
77 Claims
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1. A method for computer-aided interchange of cryptographic keys between a first computer unit and a second computer unit, which comprises:
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in the first computer unit, forming a first value from a first random number using a generating element of a finite group; transmitting a first message, which at least contains the first value, from the first computer unit to the second computer unit; in the second computer unit, forming a session key using a first hash function;
a first input variable for the first hash function including at least one first term that is formed by exponentiation of the first value using a secret network key;in the first computer unit, forming the session key using the first hash function;
a second input variable for the first hash function including at least one second term that is formed by exponentiation of a public network key using the first random number;in the first computer unit, forming a fourth input variable using a given hash function selected from the group consisting of the first hash function and a second hash function;
a third input variable for the given hash function including, for forming the fourth input variable, at least one variable that can be used to unambiguously infer the session key, at least part of the at least one variable being a nonpublic variable;in the first computer unit, using a first signature function to form a signature term from at least the fourth input variable; transmitting a third message, which at least includes the signature term, from the first computer unit to the second computer unit; and in the second computer unit, verifying the signature term. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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39. A configuration for computer-aided interchange of cryptographic keys between a first computer unit and a second computer unit, comprising:
a first computer unit and a second computer unit configured such that; the first computer unit forms a first value from a first random number using a generating element of a finite group, the first computer unit transmits a first message from the first computer unit to the second computer unit, the first message includes at least the first value, the second computer unit forms a session key using a first hash function, a first input variable for the first hash function includes at least one first term formed by exponentiation of the first value using a secret network key, the first computer unit forms the session key using the first hash function, a second input variable for the first hash function includes at least one second term formed by exponentiation of a public network key using the first random number, the first computer unit forms a fourth input variable using a given hash function selected from the group consisting of the first hash function and a second hash function, a third input variable for the given hash function including, for forming the fourth input variable, at least one variable that can be used to unambiguously infer the session key, at least part of the at least one variable being a nonpublic variable, the first computer unit uses a first signature function to form a signature term from at least the fourth input variable, the first computer unit transmits a third message to the second computer unit, the third message including at least the signature term from the first computer unit, and the second computer unit verifies the signature term. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77)
Specification