Sept. 10: This post has been updated.

Citing concerns about linking to classified material, Johns Hopkins University asked a professor this morning to remove a blog post discussing  last week’s revelations about the NSA’s efforts to break encryption. The post had linked to government documents published by ProPublica, the Guardian, and the New York Times.  

Several hours later, after computer science professor Matthew Green tweeted about the request, the university reversed itself.

Baltimore-based Johns Hopkins, which is short drive from the NSA’s headquarters at Fort Meade, works closely with the spy agency.

The university’s Applied Physics Laboratory, which employs about 5,000 people, does many projects with the NSA. 

According to the lab’s website, “APL staff working with NSA are engaged in strategic planning, development of enterprise and program architectures, conducting quantitative analysis to support engineering decisions, development of engineering processes, and formulation of the governance structures for the work in the new Technology Directorate (TD).”

The website also notes that the lab “completed a strategic study that analyzed NSA’s global information technology infrastructure to determine the top locations for the large-scale data centers.”

Green said on Twitter that he had “been told” that someone from the Applied Physics Laboratory had first flagged his blog post.

Asked about the Applied Physics Laboratory’s role, Hopkins spokesman Dennis O'Shea said, “We are still tracing the path of this event, which all exploded into our notice over the past couple of hours. So I don’t think we’re ready yet with an answer on that.”

In an earlier statement, O’Shea said: “The university received information this morning that Matthew Green’s blog contained a link or links to classified material and also used the NSA logo. For that reason, we asked Professor Green to remove the Johns Hopkins-hosted mirror site for his blog.”

He continued: “Upon further review, we note that the NSA logo has been removed and that he appears to link to material that has been published in the news media. Interim Dean Andrew Douglas will inform Professor Green that the mirror site may be restored.”

Green removed the post from his university site but it remained mirrored on Google’s blogger service. Green has since removed the agency’s logo from the post on his blog.

An expert in the field of cryptography, Green was quoted in the story published by ProPublica and the New York Times.

In his blog post, Green linked to a document that outlines the NSA’s SIGINT Enabling Project, a program focused on subverting encryption products. The document is marked Top Secret and was part of the cache taken by former NSA contractor Edward Snowden.

Green added in the post that he has not seen documents beyond the ones published with the story last week. 

Update Sept. 10: This afternoon Matthew Green received an apology from the dean who had asked him to remove the NSA blog post, Andrew Douglas of the Hopkins engineering school:

I write to apologize for any difficulty I caused you yesterday over the post on your blog.  I realize now that I acted too quickly, on the basis of inadequate and – as it turns out – incorrect information.  I requested that you take down the post without adequately checking that information and without first providing you with an opportunity to correct it.

As an academic and as a member of the faculty at Johns Hopkins for 30 years, I am wholly supportive of academic freedom and keenly aware of its centrality to our enterprise.  It is for this reason that I attached the 1940 AAUP Statement of Principles on Academic Freedom and Tenure.

Moreover, as interim dean of the Whiting School of Engineering, I am also aware of the contributions you are making to your field of information security and of the relevance of your comments to the important public debate that is now under way.

I am sorry that my request to you yesterday may have, in some minds, undeservedly undercut your reputation as a scholar and scientist.  I am also sorry if I have raised in anyone’s mind a question as to my commitment to academic freedom.  I am pleased that we were able to correct the error quickly.

I hope that you understand that my motivation – again, based on inadequate information – was to protect the university and you from legal consequences.  I look forward to discussing your work with you, as you suggested yesterday.

Separately, a Hopkins spokesman confirmed to ProPublica that someone from the Applied Physics Laboratory, which works closely with the NSA, had originally flagged Green’s post.

“[T]he federal government was not involved,” said spokesman Dennis O’Shea in an email. “The blog post originally was spotted by someone at the Johns Hopkins Applied Physics Laboratory. A message was sent from a staff member at APL to a staff member at the Homewood campus calling attention to the post. That message may have been understood as a request for action, though I am told it was intended only as an FYI. The Homewood staff member called the post to the attention of the dean. The dean wrote to Professor Green, and you know the rest.”