A method of securely using a first tenant secret key stored under an encrypted form in a first token (TKA) of a first tenant (A) identified by a first tenant identifier (UID A ) and having said first tenant secret key, wherein : each tenant identifier (UID T ) for a tenant (T) comprises a first value and, when said tenant (T) is allowed to use a secret key of a parent tenant (T P ) identified by a parent tenant identifier (UID TP ), said parent tenant identifier, appended before said first value, the method comprising the following step performed by a secure device : - generating said first token (TKA) from said first tenant identifier (UID A ) and a first tenant secret key encrypted with said first tenant identifier (UID A ) and with a first tenant customer master key (CMK A ), said first tenant customer master key (CMK A ) having been derived from said first tenant identifier (UID A ) and a secure domain master key (SDMK), said method comprising further the following steps performed by the secure device storing said secure domain master key (SDMK), on request of a second tenant (B) identified by a second tenant identifier (UID B ) : - getting said first tenant identifier (UID A ) of said first tenant (A) from said first token (TKA), - checking if the first tenant identifier (UID A ) is a prefix of or is equal to said second tenant identifier (UID B ), - when said first tenant identifier (UID A ) is a prefix of or is equal to said second tenant identifier (UID B ), recovering said first tenant secret key stored in said first token (TKA) and using it for the second tenant (B). each tenant identifier (UID T ) for a tenant (T) comprises a first value and, when said tenant (T) is allowed to use a secret key of a parent tenant (T P ) identified by a parent tenant identifier (UID TP ), said parent tenant identifier, appended before said first value, the method comprising the following step performed by a secure device : - generating said first token (TKA) from said first tenant identifier (UID A ) and a first tenant secret key encrypted with said first tenant identifier (UID A ) and with a first tenant customer master key (CMK A ), said first tenant customer master key (CMK A ) having been derived from said first tenant identifier (UID A ) and a secure domain master key (SDMK), - generating said first token (TKA) from said first tenant identifier (UID A ) and a first tenant secret key encrypted with said first tenant identifier (UID A ) and with a first tenant customer master key (CMK A ), said first tenant customer master key (CMK A ) having been derived from said first tenant identifier (UID A ) and a secure domain master key (SDMK), said method comprising further the following steps performed by the secure device storing said secure domain master key (SDMK), on request of a second tenant (B) identified by a second tenant identifier (UID B ) : - getting said first tenant identifier (UID A ) of said first tenant (A) from said first token (TKA), - checking if the first tenant identifier (UID A ) is a prefix of or is equal to said second tenant identifier (UID B ), - when said first tenant identifier (UID A ) is a prefix of or is equal to said second tenant identifier (UID B ), recovering said first tenant secret key stored in said first token (TKA) and using it for the second tenant (B). - getting said first tenant identifier (UID A ) of said first tenant (A) from said first token (TKA), - checking if the first tenant identifier (UID A ) is a prefix of or is equal to said second tenant identifier (UID B ), - when said first tenant identifier (UID A ) is a prefix of or is equal to said second tenant identifier (UID B ), recovering said first tenant secret key stored in said first token (TKA) and using it for the second tenant (B). <EOS>