Cipher block chaining data obfuscation

A computer program product comprising a nontransitory storage medium, the computer program product including code that, when executed by processing circuitry of a user device configured to perform a cipher block chaining (CBC) mode decryption operation on a plurality of blocks of ciphertext data, causes the processing circuitry to perform a method, the method comprising:

• receiving a stream of data including the plurality of blocks of ciphertext data, each of the plurality of blocks of ciphertext data having been generated using a CBC mode encryption operation on a respective block of original plaintext data of a plurality of blocks of plaintext data, each of the plurality of blocks of plaintext data being readable by the user device;
• generating a set of obfuscation pads;
• prior to completing the CBC mode decryption operation on the block of ciphertext data, performing an obfuscation operation on an obfuscation pad of the set of obfuscation pads during the CBC mode decryption operation to produce, as an output of the CBC mode decryption operation on the block of ciphertext data, a block of obfuscated plaintext data of a plurality of blocks of obfuscated data, the plurality of blocks of obfuscated plaintext data being unreadable by the user device;
• storing the block of obfuscated plaintext data in a storage device accessible to the user device;
• and
• obtaining a decryption key function that, when operating on the block of ciphertext data and a respective key, produces a keystring, and
• wherein the performing the obfuscation operation on the obfuscation pad during the CBC mode decryption operation includes performing a combination operation on a previous block of ciphertext data and the obfuscation pad to produce an obfuscated cipherblock.

An electronic apparatus configured to perform a cipher block chaining (CBC) mode decryption operation on a plurality of blocks of ciphertext data, the electronic apparatus comprising:

• a memory;
• and
• controlling circuitry coupled to the memory, the controlling circuitry configured to:
• receive a stream of data including the plurality of blocks of ciphertext data, each of the plurality of blocks of ciphertext data having been generated using a CBC mode encryption operation on a respective block of original plaintext data of a plurality of blocks of plaintext data, each of the plurality of blocks of plaintext data being readable by the user device;
• generate a set of obfuscation pads;
• prior to completing the CBC mode decryption operation on the block of ciphertext data, perform an obfuscation operation on an obfuscation pad of the set of obfuscation pads during the CBC mode decryption operation to produce, as an output of the CBC mode decryption operation on the block of ciphertext data, a block of obfuscated plaintext data of a plurality of blocks of obfuscated data, the plurality of blocks of obfuscated plaintext data being unreadable by the user device;
• store the block of obfuscated plaintext data in a storage device accessible to the user device;
• and
• obtain a decryption key function that, when operating on the block of ciphertext data and a respective key, produces a keystring, and
• wherein the controlling circuitry configured to perform the obfuscation operation on the obfuscation pad during the CBC mode decryption operation is further configured to perform a combination operation on a previous block of ciphertext data and the obfuscation pad to produce an obfuscated cipherblock.