NTRUEncrypt
The NTRUEncrypt public key cryptosystem, also known as the NTRU encryption algorithm, is a lattice-based alternative to RSA and ECC and is based on the shortest vector problem in a lattice (i.e. is not known to be breakable using quantum computers). Operations are based on objects in a truncated polynomial ring with convolution multiplication and all polynomials in the ring have integer coefficients and degree at most N-1:
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