## Introduction

09/Dec/2020, "Photonic Quantum Computer Displays 'Supremacy' Over Supercomputers", a news from spectrum.ieee.org. It clearly shows that billions value on bitcoin network is facing the threat of Quantum computers. It is time to build a Post-Quantum security cryptocurrency.
Tidecoin is an attempt to build a quantum secure cryptocurrency.

Tidecoin is a peer-to-peer Internet currency that enables instant, near-zero cost payments to anyone in the world. Tidecoin is an open source global payment network, and fully decentralized without any central authorities. Features of Post-Quantum security make Tidecoin as a replacement to Bitcoin. Tidecoin's new cryptography algorithm of Falcon is an lattice-based cryptography algorithm and based on the theoretical framework of Gentry, Peikert and Vaikuntanathan. There is no efficient solving algorithm currently known in the general case, even with the help of quantum computers, because the underlying hard problem is the short integer solution problem (SIS) over NTRU lattices.

## Features

The feature of Tidecoin.

NIST's Post-Quantum security standard
Open Source Software
Total supply: 21000000 TDC
Pow only consencus, no pre-mined, no ico
Segwit supported, reduce block size largely
One minute block time, faster payment
CPU friendly Pow algorithm, more inclusive
Exponential increase halving time：0.5, 1, 2, 4, ...Years
## Post-Quantum security signature algorithm

Falcon - Fast-Fourier Lattice-based Compact Signatures over NTRU. Falcon follows a framework introduced in 2008 by Gentry, Peikert, and Vaikuntanathan, the high-level idea is the following:

The public key is a long basis of a q-ary lattice. The private key is (essentially) a short basis of the same lattice.
In the signing procedure, the signer:

Generates a random value salt
Computes a target c=H(msg||salt), where H is a hash function sending an input to a random-looking point (on the grid)
Uses his knowledge of a short basis to compute a lattice point v close to the target c
Outputs (salt, s), where s=c−v
In the verifying procedure, The verifier accepts the signature (salt, s)

if and only if the vector s is short
H(msg||salt) −s is a point on the lattice generated by his public key.
Falcon offers the following features:

Security: a true Gaussian sampler is used internally, which guarantees negligible leakage of information on the secret key up to a practically infinite number of signatures (more than 264). To give a point of comparison, Falcon-512 is roughly equivalent,
in classical security terms, to RSA-2048, whose signatures and public keys use 256 bytes each.
Compactness: thanks to the use of NTRU lattices, signatures are substantially shorter than in any lattice-based signature scheme with the same security guarantees, while the public keys are around the same size.
Speed: use of fast Fourier sampling allows for very fast implementations, in the thousands of signatures per second on a common computer; verification is five to ten times faster.
Scalability: operations have cost O (n log n) for degree n, allowing the use of very long-term security parameters at moderate cost.
RAM Economy: the enhanced key generation algorithm of Falcon uses less than 30 kilobytes of RAM, a hundredfold improvement over previous design such as NTRU Sign. Falcon is compatible with small, memory-constrained embedded devices.