Keys
The key
type in LIGO is used for Tezos public keys. Do not confuse
them with map keys. Keys are made by casting strings. Beware of
failure if the key is invalid.
Here is how you can define a key.
const my_key : key =
"edpkuBknW28nW72KG6RoHtYW7p12T6GKc7nAbwYX5m8Wd9sDVC9yav" as key;