-ring = { version = "0.17", default-features = false, features = ["alloc"] }
-hex_lit = { version = "0.1", default-features = false, features = ["rust_v_1_46"] }
+ring = { version = "0.17", default-features = false, features = ["alloc"], optional = true }
+bitcoin_hashes = { version = "0.14", default-features = false, optional = true }
+hex_lit = { version = "0.1", default-features = false, features = ["rust_v_1_46"], optional = true }
+tokio_crate = { package = "tokio", version = "1.0", default-features = false, optional = true }
+
+[target.'cfg(fuzzing)'.dependencies]
+ibig = { version = "0.3", optional = true }