Shared secret data production with use of concealed cloaking elements

A device configured to share secret data with a second device, the device comprising:

• a memory;
• a transceiver;
• and
• a processor configured to:
• produce or receive a first public key of the device and store the first public key of the device in the memory;
• produce or receive a first public key of the second device and store the first public key of the second device in the memory;
• produce a private key of the device and its inverse based on the first public key of the device and store the private key of the device and its inverse in the memory;
• produce a second public key of the device based on the private key of the device and the first public key of the second device and store the second public key of the device in the memory;
• transmit, by the transceiver, the second public key of the device to the second device;
• receive, by the transceiver, a second public key of the second device from the second device and store the second public key of the second device in the memory, wherein the second public key of the second device is produced from a private key of the second device and the first public key of the device;
• and
• produce the shared secret data based on the private key of the device and the second public key of the second device.

A system comprising:

• a first device configured to:
• receive a first public key of a second device;
• produce a first public key of the first device based on the first public key of the second device by performing processing comprising selecting a member of a subgroup of elements that commute with the received first public key of the second device using an output of a pseudorandom number generator;
• and
• transmit the first public key to the second device;
• and
• the second device configured to:
• produce a private key of the second device and its inverse based on a first public key of the second device by performing processing comprising finding an inverse image of the first public key of the second device under a homomorphism from a group to a second group that contains the first public key of the second device and taking the inverse of said inverse image;
• produce a second public key of the second device based on the private key of the second device and a first public key of the first device by performing processing comprising:
• receiving or producing at least one cloaking element that stabilizes the first public key of the first device;
• receiving a security level (SL) for the shared secret data;
• and
• inserting a plurality of additional cloaking elements within the private key of the second device at a plurality of pseudorandom points to produce the second public key of the second device so that any recovery process to recover the private key of the second device from the second public key of the second device requires at least 2SL operations;
• transmit the second public key of the second device to the first device;
• wherein the first device is further configured to:
• produce a private key of the first device and its inverse based on the first public key of the first device by performing processing comprising finding an inverse image of the first public key of the first device under a homomorphism from a group to a second group that contains the first public key of the first device and taking the inverse of said inverse image;
• produce a second public key of the first device based on the private key of the first device and the first public key of the second device by performing processing comprising:
• receiving or producing at least one second cloaking element that stabilizes the first public key of the second device;
• receiving a security level (SL) for the shared secret data;
• and
• inserting a second plurality of additional cloaking elements within the private key of the first device at a plurality of pseudorandom points to produce the second public key of the first device so that any recovery process to recover the private key of the first device from the second public key of the first device requires at least 2SL operations;
• transmit the second public key of the first device to the second device;
• and
• produce the shared secret data based on the private key of the first device and the second public key of the second device by performing processing comprising:
• performing group element multiplication on the private key of the first device and the second public key of the second device to produce an output;
• performing E-multiplication on the output, thereby obtaining an output of the E-multiplication including a first component;
• and
• applying a cryptographic hash function on the first component of the output of the E-multiplication;
• and
• wherein the second device is further configured to produce the shared secret data based on the private key of the second device and the second public key of the first device by performing processing comprising:
• performing group element multiplication on the private key of the second device and the second public key of the first device to produce a second output;
• performing a second E-multiplication on the second output, thereby obtaining an output of the second E-multiplication including a first component;
• and
• producing an inverse of the first component of the output of the second E-multiplication;
• and
• applying a cryptographic hash function on the inverse of the first component of the output of the second E-multiplication.