ParagonIE_Sodium_Compat::crypto_sign_ed25519_sk_to_curve25519( string $sk ): string

3352    public static function crypto_sign_ed25519_sk_to_curve25519(3353        #[\SensitiveParameter]3354        $sk3355    ) {3356        /* Type checks: */3357        ParagonIE_Sodium_Core_Util::declareScalarType($sk, 'string', 1);3358 3359        /* Input validation: */3360        if (ParagonIE_Sodium_Core_Util::strlen($sk) < self::CRYPTO_SIGN_SEEDBYTES) {3361            throw new SodiumException('Argument 1 must be at least CRYPTO_SIGN_SEEDBYTES long.');3362        }3363        if (self::useNewSodiumAPI()) {3364            if (is_callable('crypto_sign_ed25519_sk_to_curve25519')) {3365                return sodium_crypto_sign_ed25519_sk_to_curve25519($sk);3366            }3367        }3368        if (self::use_fallback('crypto_sign_ed25519_sk_to_curve25519')) {3369            return (string) call_user_func('\\Sodium\\crypto_sign_ed25519_sk_to_curve25519', $sk);3370        }3371 3372        $h = hash('sha512', ParagonIE_Sodium_Core_Util::substr($sk, 0, 32), true);3373        $h[0] = ParagonIE_Sodium_Core_Util::intToChr(3374            ParagonIE_Sodium_Core_Util::chrToInt($h[0]) & 2483375        );3376        $h[31] = ParagonIE_Sodium_Core_Util::intToChr(3377            (ParagonIE_Sodium_Core_Util::chrToInt($h[31]) & 127) | 643378        );3379        return ParagonIE_Sodium_Core_Util::substr($h, 0, 32);3380    }