Robert Delgado Jr. of Monterey Park was on parole for identity theft when he participated in the second case, officials said.
The 40-year-old pleaded guilty in May to conspiracy to commit bank fraud. Delgado admitted to taking part in a scheme in which he and others impersonated victims and used their credit cards to shop at stores, such as JCPenny.
Authorities said at the time of his arrest in March, Delgado tried to hide an external hard drive that contained names, addresses, birth dates and Social Security numbers of more than 300,000 victims.
The hard drive also contained images used to make copies of California Department of Motor Vehicle ID cards and credit cards.
Three other men have pleaded guilty in the case and are awaiting sentencing.