ERROR: must be superuser to read files et pgcrypto

bonjour,

je tente d' utiliser les functions pg_crypto  , j’ai une erreur "*ERROR:
must be superuser to read files" **
*

un "GRANT EXECUTE ON ALL FUNCTIONS IN SCHEMA public TO ftuser;" ne
change rien**

quelqu'un a t il eu ce type de problème ? Merci

postgres 9.5.16 on linux

psql -h localhost -p 5432 -d FT_DB -U ftuser
Password for user ftuser:
psql (9.5.16)
Type "help" for help.

*FT_DB=> select
ft_decrypt_pwd(password,'3B259A9A610271EC2F07A6E557FBE1DA05770E44') from
ft_user;**
**ERROR:  must be superuser to read files**
**CONTEXT:  PL/pgSQL function ft_decrypt_pwd(bytea,text) line 8 at
assignment**
*