31 results about "Chosen-ciphertext attack" patented technology

There is provided a method for realizing identity-based broadcast encryption by ciphertext-policy attribute-based encryption. The steps of the method are as follows: in step 1, a PKG (Private Key Generator) inputs a safety coefficient of a system to output an initialization parameter; in step 2, the PKG runs a random number generation algorithm to choose a random number required for the system; in step 3, the PKG executes operation to obtain a public key and a master secret key; in step 4, an encrypting party chooses the random number and completes operation to output a part of ciphertext; in step 5, the encrypting party executes calculation according to a set of identities of decrypting users to obtain the remaining part of the ciphertext; in step 6, the PKG runs a random number generation algorithm to obtain a random parameter; in step 7, the PKG executes calculation according to the master secret key and the identity of the user to obtain a private key SKID; in step 8, a decrypting party conforming to requirement is able to execute calculation according to the private key and the ciphertext to obtain K; and in step 9, the decrypting user is able to output correct plaintext by executing calculation according to the K. According to the invention, a development cycle and system load are reduced greatly, and chosen ciphertext attack can be resisted, which ensures safety and effectiveness of the scheme.

The public-key encryption method uses the sender-side apparatus by the creator of a ciphertest and creates the ciphertext of a plaintext x (ε{0, 1}ⁿ) in y₁=f (x0^k1G(r)), y₂=H (x0^k1G(r))r with respect to the published trapdoor-equipped unidirectional function f and the random functions G, H. Meanwhile, the receiver of the ciphertext, who has received the ciphertext by the receiver-side apparatus via the communications line, performs the decryption processing with the use of f⁻¹, i.e., the secret key, in accordance with the steps inverse to those of the encryption processing.

The invention belongs to the technical field of information security and particularly relates to a color image encryption method based on a hybrid domain and an LSS type coupled map lattice. The method comprises the steps of inputting a color plaintext image, separating red, green and blue three primary color components of the plaintext image to obtain corresponding three matrixes, generating a parameter and an initial value of the LSS type coupled map lattice through combination of a key, and generating key streams through utilization of the LSS type coupled map lattice; carrying out two-dimensional discrete wavelet transform on the three matrixes to obtain three groups of sub-bands; keeping a high and low frequency sub-band unchanged, scrambling the other sub-bands through utilization ofthe key streams, and shrinking the scrambled sub-bands; switching the content of the shrunk sub-bands; carrying out the two-dimensional discrete wavelet transform on the three groups of sub-bands toobtain three encryption components; and blocking the three encryption components, and carrying out bit level diffusion operation on the blocked matrixes through utilization of the key streams to obtain a ciphertext image. According to the method, statistics attacks, known and chosen plaintext attacks and chosen ciphertext attacks can be effectively resisted.

There exist numerous public key probabilistic encryption algorithms. Most of these algorithms do not have a maximum security level against someone capable of chosen ciphertext attacks. The disclosed method provides a construct to enhance the security of any public key probabilistic or deterministic encryption algorithm to achieve an optimal security level.

Embodiments of the invention provide an encryption method, a decryption method and electronic equipment. The method comprises steps of acquiring a public key, a plaintext and a first bit string of a preset length through first electronic equipment, wherein the public key comprises the only defect trapdoor function; acquiring a key pair of a one-time signature scheme by the first electronic equipment, wherein the public pair comprises a verification secret key and a signature secret key corresponding to the verification secret key; acquiring a middle cryptograph set according to the only defect trapdoor function, the first bit string of the preset length, the plaintext and the verification secret key; signing the middle cryptograph set by the first electronic equipment according to the signature secret key, and acquiring a signature of the middle cryptograph set; and forming a final cryptograph by combing the verification secret key, the middle cryptograph set and the signature of the middle cryptograph set, and outputting the final cryptograph. Therefore, anti-selection cryptograph attack is achieved.

A public-key cryptographic scheme of high efficiency capable of verifying security in a standard model. In order to retain security against adaptive chosen ciphertext attacks, a ciphertext is generated by a combination of a plaintext and random numbers so that an illegal ciphertext input to a (simulated) deciphering oracle is rejected.

The invention provides a secure revocable multi-center large attribute domain attribute-based encryption method in fog computing, belonging to the field of encryption. The method includes the following steps: constructing a global parameter Param; taking the global parameter Param and an authority theta index as the input to obtain a public key PKtheta and a private key SKtheta; generating a private key SKGID, att for a user GID with an attribute expressed by a FORMULA (as shown in the original specification); taking a revocation list (RL) as the input at the authority theta to obtain {KUtheta, N}, and generating a re-encrypted key RKtheta for all unrevoked users with the attribute T(att)=theta in fog; taking a message M, an access policy (A, delta) and the key PKtheta of the authority asthe input to obtain a ciphertext C, and verifying the validity of the ciphertext C; and calculating the ciphertext C in fog to obtain a re-encrypted ciphertext C', and storing the obtained re-encrypted ciphertext in fog. The flexible fine-grained access control in fog computing can be implemented, and large attribute domains can be supported to meet various requirements in practical applications of fog computing, so that the scheme of the invention is applicable to the efficient revocation for the keys of resource-constrained devices in fog computing, and has the security of resisting chosen-ciphertext attacks.

The invention provides a plaintext-associated fractional order chaotic image encryption method. Firstly, the adopted chaotic system is a four-dimensional fractional order chaotic system, and comparedwith the chaotic system, the chaotic system is more complex in dynamic characteristic, larger in key space and more advantageous in encryption. Secondly, for most existing plaintext association encryption algorithms, the algorithm is only related to plaintext in a diffusion stage or a scrambling stage; in order to further improve the plaintext attack resistance, the image encryption method provided by the invention not only relates to image pixel diffusion and plaintext, but also relates to image position scrambling and plaintext, the image pixel diffusion adopts a secondary key plaintext association encryption algorithm, and the image position scrambling adopts a plaintext association image encryption algorithm. Experimental simulation shows that the method not only can well resist statistical property analysis, but also can effectively resist plaintext selection attacks and ciphertext selection attacks.

Provided is a verifiable public key encryption method. The encryption method includes steps: initialization, encryption, and decryption. In terms of security, the method has a mathematics hypothesis with dual difficulties referring to factorization and Diffie-Hellman problem. In other words, an attacker has to simultaneously solve the mathematical problem of the two calculations if he wants to crack the encryption method. The encryption method is designed by partly employing the concept of the trapdoor one-way function, the method has semantic security and can resist chosen plaintext attack and chosen ciphertext attack, and good practical values are provided.

The invention discloses a method for encrypting a public key in a signed quadratic residue class group. The method comprises the steps of 1, setting system parameters; 2, generating a secret key; 3, selecting a random number by a sender, carrying out encryption on a message, and generating a ciphertext data packet; 4, sending the ciphertext data packet to a receiver by the sender through a public channel; and 5, verifying the effectiveness of the ciphertext after the receiver receives the ciphertext data packet, decrypting the ciphertext data packet by using a private key, and acquiring the message. The method disclosed by the invention satisfies the confidentiality, the integrity and the chosen-ciphertext attack security simultaneously, and realizes public verification of the ciphertext legitimacy; the method does not use bilinear pairings and one-time signatures which are time-consuming, so that defects of other public key encryption methods in which the ciphertext legitimacy is verified by using the bilinear pairings and the one-time signatures are overcome, thereby having higher computational efficiency and higher practical values.

The invention relates to a pixel position and bit dual scrambling image encryption method based on AFD adaptive decomposition, which comprises the following steps: firstly, performing adaptive decomposition on a source image through an AFD method to generate two groups of key streams, and then performing pixel position scrambling and pixel bit scrambling operations on a plaintext image. The source image adopted by the method can be any image on the network or a newly generated image, the size of the source image is kept consistent with that of a plaintext image, the obtained encrypted image can efficiently resist selected plaintext attack, selected ciphertext attack and statistical attack, meanwhile, the invention has high robustness to noise attack and shearing attack. The method can indirectly realize the one-time pad encryption effect, further improves the security and robustness of the encrypted image, and can be applied to the fields of image security and image secret communication.

The invention relates to a plaintext related image encryption method based on PUD adaptive decomposition, and the method comprises the steps: carrying out the adaptive PUD decomposition of a plaintextimage, and carrying out the scrambling diffusion of a decomposed two-dimensional component. According to the method, the adopted encryption key is related to the plaintext, the obtained encrypted image can efficiently resist the attack of the selected plaintext and the attack of the selected ciphertext; meanwhile, the robustness in the aspects of filtering noise attacks, shearing attacks and differential attacks is high, and the security and robustness of the encrypted image are further improved. The method can be applied to the fields of image security and image secret communication.

The invention discloses a rerandomizable identifier encryption and decryption method, and aims to solve the security defect of an existing rerandomizable identifier encryption and decryption method. According to the invention, the technical scheme is that the method comprises the steps: constructing an encryption and decryption system composed of an initialization module, a key extraction module,an encryption module, a decryption module and a re-random module; enabling the key generation center to operate the initialization module, generating a public parameter and a main private key, and disclosing the public parameter; enabling the key generation center to operate a key extraction module, and generating a private key for the receiver by adopting the identifier id of the receiver; enabling a sender to operate the encryption module, generating a ciphertext C by adopting the identifier id of the receiver, and sending the ciphertext C to the public server; enabling a public server to operate a re-randomization module to re-randomize the C, and sending the new ciphertext C' to a receiver; and enabling a receiver to operate the decryption module to decrypt the C'. According to the invention, the replayable selective ciphertext attack based on the identifier can be resisted, and the operation of the rerandom module does not need the identifier of a receiver, so the distribution ofthe identifier is avoided.

The invention discloses a SM2-based multi-receiver public key encryption method. A traditional multi-receiver public key encryption method depends on a traditional public key encryption method, and has the defects of low encryption efficiency and high communication bandwidth requirement. Aiming at the defects, the invention provides the SM2-based multi-receiver public key encryption method for random number reuse, so that the method has the advantages of high encryption efficiency and low communication bandwidth requirement. A sender may encrypt a message into a ciphertext by using the method,and broadcasts the ciphertext to a plurality of receivers in a network; after receiving the ciphertext, the receivers can decrypt the ciphertext through a private key to obtain the message of the sender. According to the method, formalization proves that the safety of the RR-IND-CCA can be achieved, the calculated amount of the sender can be effectively reduced, and the actual work application requirements in the aspects of safety and efficiency are met.