What is the test for a conspiracy to commit a criminal conspiracy?

We recognize, of course, that "[a] conspiracy by its very nature is a secretive operation," United States v. Provenzano, 615 F.2d 37, 45 (2d Cir.), cert. denied, 446 U.S. 953, 100 S.Ct. 2921, 64 L.Ed.2d 810 (1980), and that the "[e]xistence of and participation in a conspiracy ... may be established ... through circumstantial evidence." United States v. Sanzo, 673 F.2d 64, 69 (2d Cir.), cert. denied, 459 U.S. 858, 103 S.Ct. 128, 74 L.Ed.2d 111 (1982) (emphasis added). However, there must be some evidence from which it can reasonably be inferred that the person charged with conspiracy knew of the existence of the scheme alleged in the indictment and knowingly joined and participated in it. United States v. Soto, 716 F.2d 989, 991 (2d Cir.1983). Further, " '[w]here the crime charged is conspiracy, a conviction cannot be sustained unless the Government establishes beyond a reasonable doubt that the defendant had the specific intent to violate the substantive statute[s].' " Soto, 716 F.2d at 993 (quoting United States v. Cangiano, 491 F.2d 906, 909 (2d Cir.), cert. denied, 419 U.S. 904, 95 S.Ct. 204, 42 L.Ed.2d 162 (1974)).