Cross system secure logon

A method for a cross system secure logon in a target system by using a first authentication system and a second authentication system may be provided. A correct password may be valid on the first authentication system and the second authentication system. The method may comprise receiving an input password, generating a first hash key by using the first authentication system, and/or generating a second hash key by using the second authentication system, wherein each authentication system uses a system unique non-collision free hash algorithm. The method may further comprise comparing the first hash key with a first predefined hash key of the correct password stored in the first authentication system, and/or comparing the second hash key with a second predefined hash key of the correct password stored in the second authentication system. Furthermore, the method may comprise granting access to the target system based on at least one of the comparisons.