Method for negotiating weakened keys in encryption systems

Apparatus for permitting encrypted communications between two stations which are operable with compatible encryption algorithms that accept encryption keys having work factors with respectively different values, the apparatus comprising:

• means for determining lower one of the work factor values;
• means for providing an initial encryption key having a first work factor value;
• means for comparing the first work factor value with the lower one of the work factor values;
• means for performing a hash function on a first word that includes the initial encryption key to produce an intermediate key, and deriving from the intermediate key a modified intermediate key having a work factor value not greater than the lower one of the work factor values;
• means for performing a hash function on a second word that includes the modified intermediate key to produce a second output, and deriving from the second output a final encryption key having a work factor value not greater than the lower one of the different work factor values;
• and
• means for using the initial encryption key to encrypt communications between the two stations if the first work factor value is found to not be greater than the lower one of the work factor values, and using the final encryption key to encrypt communications between the two stations if the first work factor value is found to be greater than the lower one of the work factor values.