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SAN FRANCISCO — Square Inc., a manufacturer of mobile credit card readers, is taking an offensive stance against patent infringement accusations from a Cayman Islands-based company on a litigation spree.

Square’s lawyers at Wilson Sonsini Goodrich & Rosati filed a declaratory judgment action against Protegrity Corp. Monday in the Northern District of California. The suit seeks a judgment that Square has not violated two patents pertaining to database security.

“Square and its products have not infringed, either directly or indirectly, any claim of the ’201 or ’281 patents, and thus Square has a right to continue providing products and services without interference,” wrote Wilson Sonsini partner Stefanie Shanberg.

Protegrity, a data security firm with a large patent portfolio, has filed 19 infringement suits since 2013, two of which are proceeding in the Northern District, according to the complaint.

The suit follows the receipt of two demand letters from Protegrity’s patent counsel, Woodrow Pollack, a shareholder with the Florida firm GrayRobinson. In June, Pollack sent a letter to Square’s CEO accusing the company of infringing two patents that cover methods for processing encrypted data. The letter asked for specifications and diagrams showing how Square stores encrypted account information for its online marketplace, Square Market.

In a subsequent letter on June 17, Pollack threatened litigation if he did not receive the information within 10 days.

“I will be left with no choice but to believe you are unwilling to resolve this matter short of litigation and will be forced to advise my client to proceed accordingly in filing a lawsuit and using discovery to obtain the requested materials,” Pollack wrote. “Please govern yourself accordingly.”

A spokesman for Protegrity did not immediately respond to a request for comment. According to litigation analytics firm Lex Machina, Protegrity was also hit earlier this month with a declaratory judgment action from Cupertino-based Skyhigh Networks.

Contact the reporter at mkendall@alm.com.