1. A hypersphere-based multivariable public key encryption/decryption system, characterized in that the system contains: A. an encryption module for performing encryption processing on plaintext to be encrypted so as to form ciphertext and complete encryption, which comprises a processor and a public key transformation component, wherein, after the plaintext to be encrypted is transmitted to the processor, the processor stores the plaintext, and then transmits plaintext data to the public key transformation component; the encrypted ciphertext is obtained by respectively substituting the plaintext data into multivariable polynomials; the ciphertext is subsequently transmitted to the processor for storage; and then the processor transmits the ciphertext to decryption modules of other users; and B. a decryption module for performing decryption processing on ciphertext data transmitted from other users so as to form plaintext and complete decryption, 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 the ciphertext data is received, the ciphertext 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 decrypted plaintext; and if none of the hash values is equal to the plaintext hash redundant data, the processor outputs warning information about a decryption failure to a user.