# 0 - Constants, Variables and Notation

## 0.1 Important Constants

Constants | Description |
---|---|

10 minutes | target duration of a sub-slot |

32 blocks | target number of blocks per sub-slot |

16/64 blocks | minimum/maximum number of blocks in a slot |

4608 blocks | average number of blocks per epoch |

384 blocks | average number of blocks per sub-epoch |

64 signage points | number of signage points per sub-slot |

The above imply the following:

Implied Constants | Description |
---|---|

1 day | target time of an epoch is $10 {\ \sf min}\cdot\frac{4608{\ \sf blocks}}{32\ \sf blocks}=1440{\ \sf min}\quad (=1{ \sf day})$ |

2 hours | target time of sub-epoch |

18.75 seconds | target average block arrival time is $\frac{10{\sf\ min}}{32}=18.75 {\sf\ sec}$ |

9.375 seconds | target time between signage points is $\frac{600}{64}=9.375 {\sf\ sec}$ |

## 0.2 Important Variables

Variable | Description |
---|---|

$D\in{\mathbb N}$ | difficulty parameter. Re-calibrated once per epoch to meet target of $32$ blocks per slot |

$T\in {\mathbb N}$ | time parameter (number of VDF steps for sub-slot). Re-calibrated once per epoch to meet target of $10$ minutes per sub-slot |

## 0.3 Boxes

Objective 0:

We will use blue boxes like this one to mention key objectives we want the design of Chia to satisfy

Design Choice 0:

Green boxes like this are used to highlight important design choices, which often will refer to objectives.

Security Notice 0:

A red box stresses some important aspects required for the security of Chia, and will typically refer to some design choice.