Method and system for communicating a secret

A method of receiving a secret sent from a sender to a recipient, the method comprising:

• receiving, at the recipient, information identifying a plurality of secrets selectable by the recipient;
• sending, to the sender, from the recipient, a first public key, corresponding to a first secret of the plurality of secrets selected for access by the recipient, wherein the first public key is part of a public key/private key pair of an elliptic curve cryptography system and a first private key corresponding to the first public key is accessible to the recipient;
• sending, to the sender, from the recipient, a second public key, corresponding to a second secret of the plurality of secrets not selected for access by the recipient, wherein the second public key is a public key of said elliptic curve cryptography system and a second private key, corresponding to the second public key, is not available to the recipient;
• encrypting the first secret by means of the first public key and a third public key containing a first masking term comprising a result of scalar multiplication, by a first masking integer, known to the sender, of an elliptic curve generator point of the elliptic curve cryptography system, added to a first encryption term by means of elliptic curve point addition, wherein the first encryption term comprises a result of scalar multiplication of the elliptic curve generator point by a first encryption integer, the first encryption integer being a hash value of the first public key;
• receiving, at the recipient from the sender, the encrypted first secret;
• encrypting the second secret by means of the second public key;
• and
• receiving, at the recipient from the sender, the encrypted second secret,
• wherein the first secret is accessible to said recipient by means of the first private key, the second secret is inaccessible to said recipient, and said sender is unable to distinguish between the first secret and the second secret.

A computer implemented system, comprising a processor and a memory coupled to the processor, the memory storing thereon computer executable instructions that, when executed, cause the system to:

• send, from the sender to the recipient, information identifying a plurality of secrets selectable by the recipient;
• receive, at the sender, from the recipient, a first public key, corresponding to a first secret of the plurality of secrets selected for access by the recipient, wherein the first public key is part of a public key/private key pair of an elliptic curve cryptography system and a first private key corresponding to said first public key is accessible to the recipient;
• receive, at the sender, from the recipient, a second public key, corresponding to a second secret not selected for access by the recipient, wherein the second public key is a public key of said elliptic curve cryptography system and a second private key, corresponding to said second public key, is not available to the recipient;
• encrypt the first secret by means of the first public key and a third public key containing a first masking term comprising a result of scalar multiplication, by a first masking integer, known to the sender, of an elliptic curve generator point of the elliptic curve cryptography system, added to a first encryption term by means of elliptic curve point addition, wherein the first encryption term comprises a result of scalar multiplication of the elliptic curve generator point by a first encryption integer, the first encryption integer being a hash value of the first public key;
• send, from the sender to the recipient, the encrypted first secret;
• encrypt the second secret;
• and
• send, from the sender to the recipient, the encrypted second secret,
• wherein the first secret is accessible to said recipient by means of the corresponding first private key, the second secret is inaccessible to said recipient, and said sender is unable to distinguish between the first secret and the second secret.

A computer implemented system, comprising a processor and a memory coupled to the processor, the memory storing thereon computer executable instructions that, when executed, cause the system to:

• receive, at the recipient, information identifying a plurality of secrets selectable by the recipient;
• send, to the sender, from the recipient, a first public key, corresponding to a first secret of the plurality of secrets selected for access by the recipient, wherein the first public key is part of a public key/private key pair of an elliptic curve cryptography system and a first private key corresponding to the first public key is accessible to the recipient;
• send, to the sender, from the recipient, a second public key, corresponding to a second secret of the plurality of secrets not selected for access by the recipient, wherein the second public key is a public key of said elliptic curve cryptography system and a second private key, corresponding to the second public key, is not available to the recipient;
• encrypt the first secret by means of the first public key and a third public key containing a first masking term comprising a result of scalar multiplication, by a first masking integer, known to the sender, of an elliptic curve generator point of the elliptic curve cryptography system, added to a first encryption term by means of elliptic curve point addition, wherein the first encryption term comprises a result of scalar multiplication of the elliptic curve generator point by a first encryption integer, the first encryption integer being a hash value of the first public key;
• receive, at the recipient from the sender, the encrypted first secret;
• encrypt the second secret by means of the second public key;
• and
• receive, at the recipient from the sender, the encrypted second secret,
• wherein the first secret is accessible to said recipient by means of the first private key, the second secret is inaccessible to said recipient, and said sender is unable to distinguish between the first secret and the second secret.