I came across  and I'm very puzzled by this paper.
They use a building block which they call "identity-based dynamic threshold (IBDT) signature", citing paper .
First of all  does use this IBDT term. But even the algorithms list described in  do not match the one in . My major concern is this
Comb algorithm in  which does not appear at all in  and that apparently combines signatures with different identities to create a signature that contains all the identities required by the policy $S$.
Combining signatures to get a more powerful signature seems to be the opposite of the security properties of an Attribute-Based scheme, which is what  is about, so I was wondering if they just did not cite the proper reference. However at the same time the rest of the algorithms listed in  for IBDT is very similar to the one in .
Is there a way they are referring to another scheme ? I found paper  that seems to do what  describes, namely combining 'partial' signatures, but there does not seem to be a dynamic threshold.
 http://web.ua.es/va/recsi2014/documentos/papers/privacy-preserving-group-discounts.pdf "'Privacy-Preserving Group Discounts' by Josep Domingo-Ferrer and Alberto Blanco-Justicia"
 J. Herranz, F. Laguillaumie, B. Libert and C. Ràfols, “Short attribute-based signatures for threshold predicates,” Topics in Cryptology–CT-RSA 2012, pp. 51–67, Springer, 2012.
 Sherman S.M. Chow and Lucas C.K. Hui and S.M. Yiu, "Identity Based Threshold Ring Signature", https://eprint.iacr.org/2004/179
appendix: other concerns with this paper
The rest of  is also very surprising: While the writing style of the abstract suggests an author who is accustomed to writing papers in cryptography, the protocol description is extremely informal and weird (and the protocol seems so weak !) and the "Security analysis" only states that "the scheme is secure by design".
My guess would be that  is a bare joke but it has been published in a (very modest, it seems) conference "RECSI XIII", it is in Springer's LNCS and the first author seems to be a senior researcher who according to its personal web page received prizes, awards and so on. Apparently the paper also led to a patent and a smartphone application. Because of all this "impact" (?) I do not dare calling this paper a joke before really trying to understand what this paper really is.