1. A hypersphere-based multivariable public key encryption/decryption system, comprising: an encryption module, which comprises a processor and a public key transformation component, wherein, after a plaintext to be encrypted is transmitted to the processor, the processor stores the plaintext, and then transmits the plaintext to the public key transformation component; an encrypted ciphertext is obtained by respectively substituting the plaintext into multivariable polynomials; the encrypted ciphertext is subsequently transmitted to the processor for storage; and then the processor transmits the encrypted ciphertext to a plurality of decryption modules of other users; and a decryption module, which comprises the processor, a first affine transformation inversion component, a trapdoor component and a second affine transformation inversion component, with the trapdoor component containing a linear equation system construction component and a linear equation system solving component, wherein, after ciphertext data is received, the ciphertext data is firstly transmitted by the processor to the first affine transformation inversion component for an affine transformation inversion computation, and then transmitted to the linear equation system construction component and the linear equation system solving component of the trapdoor component respectively for a linear equation system construction computation and a linear equation system solving computation; a group of solutions obtained through the polynomial inversion computation are transmitted to the second affine transformation inversion component for an affine transformation inversion computation and are finally transmitted to the processor; for one or more sets of data transmitted, the processor respectively calculates a hash value for each set of data, if an obtained hash value of a certain set of data is equal to plaintext hash redundant data prestored in the processor, the set of data is stored and output as a decrypted plaintext; and if hash value is equal to the plaintext hash redundant data, the processor outputs warning information about a decryption failure to a user.