Hashed

Defined in: lib/provable/packed.ts:195

Hashed<T> represents a type T by its hash.

Since a hash is only a single field element, this can be more efficient in provable code where the number of constraints depends on the number of field elements per value.

For example, Provable.if(bool, x, y) takes O(n) constraints, where n is the number of field elements in x and y. With Hashed, this is reduced to O(1).

The downside is that you will pay the overhead of hashing your values, so it helps to experiment in which parts of your code a hashed representation is beneficial.

Usage:

// define a hashed type from a type
let HashedType = Hashed.create(MyType);

// hash a value
let hashed = HashedType.hash(value);

// ... operations on hashes, more efficient than on plain values ...

// unhash to get the original value
let value = hashed.unhash();

Warning: When wrapping a type with Hashed, make sure that that type is safe to automatically pack and unpack in provable code. In particular, do not use Hashed with types that define a custom toInput() (specifying a certain bit packing) but no corresponding check() method (that constrains the bit lengths of the packed parts).

Type Parameters

• T

Constructors

new Hashed()

new Hashed<T>(hash: Field, value: Unconstrained<T>): Hashed<T>

Defined in: lib/provable/packed.ts:233

Parameters

hash

Field

value

Unconstrained<T>

Returns

Hashed<T>

Properties

hash

hash: Field;

Defined in: lib/provable/packed.ts:196

---

value

value: Unconstrained<T>;

Defined in: lib/provable/packed.ts:197

---

_innerProvable

static _innerProvable: 
  | undefined
| ProvableHashable<any>;

Defined in: lib/provable/packed.ts:276

---

_provable

static _provable: 
  | undefined
| ProvableHashable<Hashed<any>>;

Defined in: lib/provable/packed.ts:275

Accessors

Constructor

Get Signature

get Constructor(): typeof Hashed

Defined in: lib/provable/packed.ts:278

Returns

typeof Hashed

---

innerProvable

Get Signature

get static innerProvable(): ProvableHashable<any>

Defined in: lib/provable/packed.ts:282

Returns

ProvableHashable<any>

Methods

toFields()

toFields(): Field[]

Defined in: lib/provable/packed.ts:270

Returns

Field[]

---

unhash()

unhash(): T

Defined in: lib/provable/packed.ts:260

Unwrap a value from its hashed variant.

Returns

T

---

_hash()

static _hash(_: any): Field

Defined in: lib/provable/packed.ts:238

Parameters

_

any

Returns

Field

---

create()

static create<T>(type: WithProvable<ProvableHashable<T>>, hash?: (t: T) => Field): typeof Hashed & {
  provable: ProvableHashable<Hashed<T>>;
  empty: Hashed<T>;
}

Defined in: lib/provable/packed.ts:202

Create a hashed representation of type. You can then use HashedType.hash(x) to wrap a value in a Hashed.

Type Parameters

• T

Parameters

type

WithProvable<ProvableHashable<T>>

hash?

(t: T) => Field

Returns

typeof Hashed & { provable: ProvableHashable<Hashed<T>>; empty: Hashed<T>; }

---

hash()

static hash<T>(value: T, hash?: Field): Hashed<T>

Defined in: lib/provable/packed.ts:251

Wrap a value, and represent it by its hash in provable code.

let hashed = HashedType.hash(value);

Optionally, if you already have the hash, you can pass it in and avoid recomputing it.

Type Parameters

• T

Parameters

value

T

hash?

Field

Returns

Hashed<T>