Methods for authenticating and/or detecting tampering of an item of interest using a nucleic acid tag. A nucleic acid tag comprising a nucleotide-support platform attached to a nucleic acid molecule is created or obtained and then sealed within or on the item of interest. The surface of the item of interest is sampled for the presence of the seeded tag after the item of interest has been moved from one location to another or has been stored for a period of time, during which tampering can occur and/or authentication may necessary. The presence of the tag can indicate that tampering has occurred, or that the item of interest is authentic.