# pubkey_encode · Rell standard library · Chromia Docs (concept)

> pure function pubkey_ encode(pubkey: byte_array , [compressed: boolean ]): byte_array Convert between public key formats. Accepts valid public keys of size

Source: https://docs.chromia.com/pages/rell-stdlib/-rell-system-library/crypto/pubkey_encode/

FUNCTION

# pubkey\_encode

```signature
pure function pubkey_encode(pubkey: byte_array, [compressed: boolean]): byte_array
```

Convert between public key formats.

Accepts valid public keys of size `33`, `64` or `65` bytes. Note that not all byte arrays of
acceptable length constitute valid public keys.

The optional boolean flag `compressed` determines whether a compressed (33-byte), or uncompressed
(65-byte) public key, is returned. Defaults to false (uncompressed) if not provided.

Examples:

Rell

```
// convert a 33-byte pubkey to a 65-byte pubkey:
crypto.pubkey_encode(my_33_byte_pubkey)
// convert a 65-byte pubkey to a 33-byte pubkey:
crypto.pubkey_encode(my_65_byte_pubkey, true)
// convert a 64-byte pubkey to a 65-byte pubkey:
crypto.pubkey_encode(my_64_byte_pubkey)
// convert a 64-byte pubkey to a 33-byte pubkey:
crypto.pubkey_encode(my_64_byte_pubkey, true)
```

Note that this function cannot return a 64-byte public key. However a 64-byte public key can be
obtained from a 65-byte public key by dropping the first byte with `byte_array.sub(1)`:

Rell

```
// convert a 65-byte pubkey to a 64-byte pubkey:
my_65_byte_pubkey.sub(1)
// convert a 33-byte pubkey to a 64-byte pubkey:
crypto.pubkey_encode(my_33_byte_pubkey).sub(1)
```

**Parameters**

* **pubkey** — the public key to compress/uncompress
* **compressed** — whether the returned public key should be compressed, defaults to false

**Returns**

a 65-byte public key in uncompressed mode, or a 33-byte public key in compressed mode

**Throws**

* `exception` — when - the given byte array does not have length `33`, `64` or `65` - the given byte array is not a valid public key

Since 0.13.5

[View this page on docs.chromia.com](https://docs.chromia.com/pages/rell-stdlib/-rell%20-system%20-library/crypto/pubkey_encode.html)Generated API reference, mirrored from the live docs