Calculate the public key from a secret key

# sodium_crypto_box_publickey_from_secretkey

(PHP 7 >= 7.2.0, PHP 8)

sodium_crypto_box_publickey_from_secretkey — Calculate the public key from a secret key

### Description

sodium_crypto_box_publickey_from_secretkey(#[\SensitiveParameter] string `$secret_key`): string

Given a secret key, calculate the corresponding public key.

This only works with the type of keys intended for use with crypto_box() (which uses Elliptic Curve Diffie-Hellman over the Montgomery curve, Curve25519; abbreviated as X25519), not crypto_sign() (which uses Edwards Digital Signature Algorithm over the Edwards Curve with the corresponding parameters; abbreviated Ed25519).

### Parameters

`secret_key`
  X25519 secret key

### Return Values

X25519 public key.

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