Security patch without changing the key

A method of producing a cryptographic implementation of a keyed cryptographic operation mapping an input message to an output message in a cryptographic system, wherein the cryptographic implementation is patchable without changing the cryptographic key, comprising:

• receiving information specifying a plurality of message groups;
• modifying the cryptographic implementation based upon the received information specifying the plurality of message groups so that:
• when a message from a first message set is received by the cryptographic implementation, the first message uses a first portion of the cryptographic implementation;
• when a second message from a second message set is received the cryptographic implementation after deciding to patch the cryptographic implementation, the second message uses a second portion of the cryptographic implementation that is not used for any messages in the first message set.

A method of mapping an input message to an output message in a cryptographic implementation of a keyed cryptographic operation in a cryptographic system, wherein the cryptographic implementation is patchable without changing the cryptographic key, comprising:

• receiving, by the cryptographic system, a first input message associated with a first message set, wherein the first message set is associated with a first portion of the cryptographic implementation;
• performing, by the cryptographic system, a keyed cryptographic operation mapping the first input message into a first output message, wherein the performing the mapping on the first input message uses the first portion of the cryptographic implementation;
• receiving, by the cryptographic system, a second input message associated with a second message set, wherein the second message set is associated with a second portion of the cryptographic implementation;
• performing, by the cryptographic system, a keyed cryptographic operation mapping the second input message into a second output message, wherein the performing the mapping on the second input message uses the second portion of the cryptographic implementation that is not used for any messages in the first message set.

A non-transitory machine-readable storage medium encoded with instructions for execution by a cryptographic implementation of a keyed cryptographic operation in a cryptographic system for mapping an input message to an output message, wherein the cryptographic implementation is patchable without changing the cryptographic key, the non-transitory machine-readable storage medium comprising:

• instructions for receiving a first input message associated with a first message set, wherein the first message set is associated with a first portion of the cryptographic implementation;
• instructions for performing a keyed cryptographic operation mapping the first input message into a first output message, wherein performing the mapping on the first input message uses the first portion of the cryptographic implementation;
• instructions for receiving a second input message associated with a second message set, wherein the second message set is associated with a second portion of the cryptographic implementation;
• instructions for performing a keyed cryptographic operation mapping the second input message into a second output message, wherein the performing the mapping on the second input message uses the second portion of the cryptographic implementation that is not used for any messages in the first message set.