Key generation utility (#176)

* RPCs for versioning.

* Build fix for bad merge.

* Add system_name RPC

* Fix tests.

* Fix demo build.

* Remove BadFormat.

* Add ss58check encoding and subkey.

* Improvements.

* Update Cargo.toml

substrate/subkey/src/main.rs

@@ -0,0 +1,55 @@
+extern crate ed25519;
+extern crate substrate_primitives;
+
+use std::env::args;
+use ed25519::Pair;
+use substrate_primitives::hexdisplay::HexDisplay;
+
+fn good_waypoint(done: u64) -> u64 {
+	match done {
+		0 ... 1_000_000 => 100_000,
+		0 ... 10_000_000 => 1_000_000,
+		0 ... 100_000_000 => 10_000_000,
+		_ => 100_000_000,
+	}
+}
+
+fn main() {
+	if args().len() != 2 {
+		println!("Usage: subkey <search string>");
+		return;
+	}
+	let desired = args().last().unwrap();
+	let score = |s: &str| {
+		for truncate in 0..desired.len() - 1 {
+			let snip_size = desired.len() - truncate;
+			let truncated = &desired[0..snip_size];
+			if let Some(pos) = s.find(truncated) {
+				return (31 - pos) + (snip_size * 32);
+			}
+		}
+		0
+	};
+	let top = 30 + (desired.len() * 32);
+	let mut best = 0;
+	let mut seed = Pair::generate().public().0;
+	let mut done = 0;
+	loop {
+		let p = Pair::from_seed(&seed);
+		let ss58 = p.public().to_ss58check();
+		let s = score(&ss58);
+		if s > best {
+			println!("{}: {} ({}% complete)", ss58, HexDisplay::from(&seed), s * 100 / top);
+			best = s;
+			if best == top {
+				break;
+			}
+		}
+		seed = p.public().0;
+		done += 1;
+
+		if done % good_waypoint(done) == 0 {
+			println!("{} keys searched", done);
+		}
+	}
+}