ZIR
ZIR is the intermediate representation ZoKrates uses to represent programs. It is close to R1CS but still encapsulates witness generation.
Note that ZIR is still in development and can change without notice.
Serialisation
ZIR programs are serialised with the following format:
| Fields | Length in bytes | Description |
|---|---|---|
| Magic | 4 | ZOK in ASCII, right-padded by 0: 0x5a4f4b00 |
| Version | 4 | This format's version, as a big endian number: 0x00000001 |
| Field size | 4 | The first 4 bytes of sha256(FIELD_MODULUS): 0xb4f7b5bd for bn128 for example |
| Program | n | The bincode-encoded program |
Display
When generating R1CS constraints, very large numbers are often used, which can make reading ZIR hard for humans.
To mitigate this, ZIR applies an isomorphism when displaying field elements: they are shown as members of the interval [- (p - 1)/2, (p - 1)/2]. In other words, the following mapping is used:
- elements in
[0, (p - 1)/2]map to themselves - elements in
[(p + 1)/2, p - 1]map to themselves minusp
Therefore, instead of writing p - 1 as:
21888242871839275222246405745257275088548364400416034343698204186575808495616
... in ZIR, we simply write:
-1