An item is encrypted to create a unique hash-value for the item. From this hash-value, an item can be uniquely identified. The hash-value for the item is stored in a first blockchain. When the item is included in a transaction, a transaction entry is stored in a block of the first blockchain. When an item participates in a group of items, a group of items is formed. The group of items is encrypted to create a unique hash-value for the group of items. The hash-value for the group of items may be based on hash-values from the items included in the group of items. The hash-value for the group of items is stored in a second blockchain that is distinct from the first blockchain. When the group of items is included in a transaction, a transaction entry is stored in a block of a second blockchain.