RANDOM.ORG's Verification Trail Service lets you save your randomizations to an immutable audit trails, such that you can prove which randomizations you performed and when.
Each randomization is saved in a trail of your choice along with its parameters and an optional comment from you. The trail entry also contains a timestamp and a verification code. Once a randomization has been saved, it is not possible to modify or delete it. For this reason, the trail can be considered an authoritative record of your randomizations.
The service supports private and public trails.