No, not arbitrary. It could have been any other technique or proof that potentially makes breaking ciphers easier, but the idea in the novel is that the proof m

No, not arbitrary. It could have been any other technique or proof that potentially makes breaking ciphers easier, but the idea in the novel is that the proof might have constructive applications or could at least lead to them, and the mathematician who developed it is specialized in the topic and not a crackpot. The decisive factor for the plot is that other agencies want to have it, though.