The private equity firm that agreed to acquire security solutions provider Entrust is challenging the company’s alternative takeover proposals.

Entrust, which makes enterprise authentication and digital signature solutions, agreed on April 13 to be acquired by Thoma Bravo, a private equity firm, for $114 million. As part of the deal, though, Dallas-based Entrust reserved the right to entertain other offers for the next 30 days.

Entrust, in a filing Wednesday with the Securities and Exchange Commission, said three third-party bidders have made bids that qualify as “superior proposals,” defined as a bid that will benefit Entrust’s stockholders more than the current bid with Thoma Bravo.

But in a letter dated Thursday, Scott Crabill, president of HAC Holdings, an affiliate of Thoma Bravo, said the company “strongly disagrees with the conclusions reached [by Entrust].”

“Due to the substantial conditionality in each of the three proposals, we believe none of them could reasonably be expected to lead to a ‘superior proposal’ or is reasonably likely to lead to a superior proposal,” he said.

In particular, he said some of the bidders were unable to identify equity financing sources, and even if they had, Entrust, per its agreement with Thoma Bravo, is prohibited from providing certain business documents to any potential funding sources. Additionally, Crabill said the time Thoma Bravo is spending to analyze these proposals is affecting its ability to close the deal.

“Entrust has a contractual obligation to work with us to get this deal closed, and we believe that diluting management’s time and attention given our deal will put the closing at risk,” he said.

If Entrust doesn’t ultimately get acquired by Thoma Bravo, it is required to pay a termination fee of $4,577,200 — but only half of that if it reaches an agreement with another company that it considered during the 30-day period.

In any event, Entrust’s shareholders still are expected to vote for the Thoma Bravo acquisition when they meet June 8. Board Chairman Michael McGrath told stockholders in a letter dated last Tuesday that the merger was fair and encouraged them to approve the deal.