System for controlling access to a function having clock synchronization

A system for authentication of individuals and/or messages, including at least one first portable unit personalized for an individual and at least one second verification unit capable of delivering an authentication function authentifying said individual and/or said messages,

• (a) said first unit comprising:
• first generating means for generating at least first and second variables,
• first calculating means for producing a first password with the aid of at least a first encryption algorithm using an encryption key for encrypting at least said first and second variables;
• transmission means for transmitting said first password to said second unit;
• (b) said second unit comprises:
• second generating means for, in response to an authentication request made by way of a specified one of said first units, generating at least third and fourth variables assigned to this first unit;
• second calculating means for producing a second password with the aid of at least one second encryption algorithm using an encryption key for encrypting at least said third and fourth variables, said first and second variables and said third and fourth variables being respectively produced in concert, but independently in said first and second units;
• means for comparing said first and second passwords;
• delivering means for, in the event of a predetermined consistency of said passwords, deliver said authentication function;
• said transmission means being configured so as to transmit with said first password n digits having the least significant weight of said first and second variables from said first unit to said second unit;
• (c) said second unit further comprising:
• j) substituting means for, based on the current value of said third and fourth variables respectively, generate first and second substituted values each wherein n digits having the least significant weight are replaced respectively by said n digits having the least significant weight of said first and second variables, said third and fourth variables thereby each comprising a replaced first group of n least significant digits and a second group of m highest significant digits;
• jj) third calculating means for:
• k) retaining respectively as third variable for the calculation of said second password said first substituted variable, if said first substituted variable and said current value of said third variable are consistent with at least a first predetermined condition,
• kk) if said first predetermined condition is not satisfied, adjusting in said first substituted value by one unit said second group of m highest significant digits, said adjusting being dependent from a second predetermined condition, said adjusting generating a first substituted and adjusted variable, and
• kkk) retaining as third variable for the calculation of said second password said first substituted and adjusted variable.
• jjj) said third calculating means being also arranged so as to:
• l) retain as fourth variable for the calculation of said second password said second substituted variable, if said second substituted variable and said current value of said fourth variable are consistent with at least a third predetermined condition,
• ll) if said third predetermined condition is not satisfied, adjust in said second substituted value by one unit said second group of m highest significant digits, said adjusting being dependent from a fourth predetermined condition, said adjusting generating a second substituted and adjusted variable, and
• lll) retain as fourth variable for the calculation of said second password said second substituted and adjusted variable.