| CPC H04L 9/3257 (2013.01) [H04L 9/008 (2013.01)] | 15 Claims |

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1. A method of generating a digital signature, the method comprising:
generating a first signature ciphertext and a message ciphertext by encrypting each of first signature information and a message by using a homomorphic encryption public key,
obtaining encrypted third signature information generated using second signature information, an element value corresponding to the second signature information, the first signature ciphertext, and the message ciphertext, and
calculating a first digital signature value included in the digital signature by using the first signature information and the second signature information, calculating a second digital signature value included in the digital signature by decrypting the encrypted third signature information, and generating the digital signature by using the calculated first digital signature value and second digital signature value.
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