Remove CRC-24 dependency. Closes #3

CHANGELOG.md

@@ -1,8 +0,0 @@
-2015-02-03:
-
-* I changed the CRC-24 checksum computation to include the coding parameter
-  K and the share number N so that these numbers are also protected.
-  If you have older shares generated with a previous version, you can still
-  decode the secret by simply removing the checksum part of the shares.
-* The README now includes more information about the inner workings of
-  secretshare and also a note on "perfect secrecy".

Cargo.lock

@@ -2,17 +2,11 @@
 name = "secretshare"
 version = "0.1.6"
 dependencies = [
- "crc24 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "getopts 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.3.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.18 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
-[[package]]
-name = "crc24"
-version = "0.1.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-
 [[package]]
 name = "getopts"
 version = "0.2.14"
@@ -20,7 +14,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "libc"
-version = "0.2.8"
+version = "0.2.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -28,7 +22,7 @@ name = "rand"
 version = "0.3.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.9 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]

Cargo.toml

@@ -9,5 +9,4 @@ readme = "README.md"
 [dependencies]
 getopts = "^0.2.14"
 rustc-serialize = "^0.3.18"
-crc24 = "^0.1.6"
 rand = "^0.3.14"

README.md

@@ -17,11 +17,11 @@ Passing a secret to secretshare for encoding:
 
 ```
 $ echo My secret | ./secretshare -e2,5
-2-1-1YAYwmOHqZ69jA-v+mz
+2-1-1YAYwmOHqZ69jA
-2-2-YJZQDGm22Y77Gw-IhSh
+2-2-YJZQDGm22Y77Gw
-2-3-+G9ovW9SAnUynQ-Elwi
+2-3-+G9ovW9SAnUynQ
-2-4-F7rAjX3UOa53KA-b2vm
+2-4-F7rAjX3UOa53KA
-2-5-j0P4PHsw4lW+rg-XyNl
+2-5-j0P4PHsw4lW+rg
 ```
 
 The parameters following the `-e` option tell `secretshare` to create 5 shares of which 2 will be necessary for decoding.
@@ -29,7 +29,7 @@ The parameters following the `-e` option tell `secretshare` to create 5 shares o
 Decoding a subset of shares (one share per line) can be done like this:
 
 ```
-$ echo -e "2-2-YJZQDGm22Y77Gw-IhSh \n 2-4-F7rAjX3UOa53KA-b2vm" | ./secretshare -d
+$ echo -e "2-2-YJZQDGm22Y77Gw \n 2-4-F7rAjX3UOa53KA" | ./secretshare -d
 My secret
 ```
 
@@ -62,9 +62,9 @@ The generated shares are lines of ASCII text.
 # Structure of the shares
 
 ```
-  2-1-LiTyeXwEP71IUA-Qj6n
+  2-1-LiTyeXwEP71IUA
-  ^ ^ ^^^^^^^^^^^^^^ ^^^^
+  ^ ^ ^^^^^^^^^^^^^^
-  K N        D        C
+  K N        D        
 ```
 
 A share is built out of three or four parts separated with a minus: K-N-D-C.
@@ -73,10 +73,7 @@ how many distinct
 shares of a specific secret are necessary to be able to recover the
 secret. The number N identifies the share (ranging from 1 to the number
 of shares that have been created). The D part is a Base64 encoding of
-a specific share's raw data. The optional part C is a Base64 encoding
+a specific share's raw data.
-of a CRC-24 checksum of the concatenation of K and N as bytes followed
-by the share's raw data (before Base64 encoding). The same checksum
-algorithm is used in the OpenPGP format for “ASCII amoring”.
 
 # A word on the secrecy
 

src/main.rs

@@ -1,6 +1,5 @@
 extern crate rustc_serialize as serialize;
 extern crate getopts;
-extern crate crc24;
 extern crate rand;
 
 use std::convert;
@@ -154,22 +153,7 @@ fn parse_k_n(s: &str) -> io::Result<(u8, u8)> {
 	Ok((k, n))
 }
 
-/// computes a CRC-24 hash over the concatenated coding parameters k, n
+fn perform_encode(k: u8, n: u8) -> io::Result<()> {
-/// and the raw share data
-fn crc24_as_bytes(k: u8, n: u8, octets: &[u8]) -> [u8; 3] {
-	use std::hash::Hasher;
-
-	let mut h = crc24::Crc24Hasher::new();
-	h.write(&[k, n]);
-	h.write(octets);
-	let v = h.finish();
-
-	[((v >> 16) & 0xFF) as u8,
-	 ((v >>  8) & 0xFF) as u8,
-	 ( v        & 0xFF) as u8]
-}
-
-fn perform_encode(k: u8, n: u8, with_checksums: bool) -> io::Result<()> {
     let secret = {
         let limit: usize = 0x10000;
         let stdin = io::stdin();
@@ -192,12 +176,7 @@ fn perform_encode(k: u8, n: u8, with_checksums: bool) -> io::Result<()> {
 	};
 	for (index, share) in shares.iter().enumerate() {
 		let salad = share.to_base64(config);
-		if with_checksums {
+		println!("{}-{}-{}", k, index+1, salad);
-			let crc_bytes = crc24_as_bytes(k, (index+1) as u8, &**share);
-			println!("{}-{}-{}-{}", k, index+1, salad, crc_bytes.to_base64(config));
-		} else {
-			println!("{}-{}-{}", k, index+1, salad);
-		}
 	}
 	Ok(())
 }
@@ -218,13 +197,12 @@ fn read_shares() -> io::Result<(u8, Vec<(u8,Vec<u8>)>)> {
 			return Err(other_io_err("Share parse error: Expected 3 or 4 \
 			                         parts searated by a minus sign", None));
 		}
-		let (k, n, p3, opt_p4) = {
+		let (k, n, p3) = {
 			let mut iter = parts.into_iter();
 			let k = try!(iter.next().unwrap().parse::<u8>().map_err(pie2io));
 			let n = try!(iter.next().unwrap().parse::<u8>().map_err(pie2io));
 			let p3 = iter.next().unwrap();
-			let opt_p4 = iter.next();
+			(k, n, p3)
-			(k, n, p3, opt_p4)
 		};
 		if k < 1 || n < 1 {
 			return Err(other_io_err("Share parse error: Illegal K,N parameters", None));
@@ -233,20 +211,6 @@ fn read_shares() -> io::Result<(u8, Vec<(u8,Vec<u8>)>)> {
 			p3.from_base64().map_err(|_| other_io_err(
 				"Share parse error: Base64 decoding of data block failed", None ))
 		);
-		if let Some(check) = opt_p4 {
-			if check.len() != 4 {
-				return Err(other_io_err("Share parse error: Checksum part is \
-				                         expected to be four characters", None));
-			}
-			let crc_bytes = try!(
-				check.from_base64().map_err(|_| other_io_err(
-					"Share parse error: Base64 decoding of checksum failed", None))
-			);
-			let mychksum = crc24_as_bytes(k, n, &*data);
-			if crc_bytes != mychksum {
-				return Err(other_io_err("Share parse error: Checksum mismatch", None));
-			}
-		}
 		if let Some((ck, cl)) = opt_k_l {
 			if ck != k || cl != data.len() {
 				return Err(other_io_err("Incompatible shares", None));
@@ -311,7 +275,7 @@ fn main() {
  		return;
 	}
 
-	let action: Result<_,_> = 
+	let action: Result<_,_> =
 		match (opt_matches.opt_present("e"), opt_matches.opt_present("d")) {
 			(false, false) => Err("Nothing to do! Use -e or -d"),
 			(true, true) => Err("Use either -e or -d and not both"),
@@ -335,7 +299,7 @@ fn main() {
 
 	let result =
 		match action {
-			Ok(Action::Encode(k,n)) => perform_encode(k, n, true),
+			Ok(Action::Encode(k,n)) => perform_encode(k, n),
 			Ok(Action::Decode) => perform_decode(),
 			Err(e) => Err(other_io_err(e, None))
 		};
@@ -345,4 +309,3 @@ fn main() {
 		// env::set_exit_status(1); // FIXME: unstable feature
 	}
 }
-