XChaCha20 support

2021-06-27 20:35:23 +02:00 · 2021-06-27 20:35:23 +02:00 · 4003185b8b
commit 4003185b8b
parent 796a01376e
9 changed files with 302 additions and 66 deletions
--- a/Cargo.lock
+++ b/Cargo.lock
@ -15,6 +15,15 @@ dependencies = [
 "opaque-debug",
 ]

+[[package]]
+name = "ansi_term"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ee49baf6cb617b853aa8d93bf420db2383fab46d314482ca2803b40d5fde979b"
+dependencies = [
+ "winapi",
+]
+
 [[package]]
 name = "argon2"
 version = "0.2.1"
@ -37,6 +46,17 @@ version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "23b62fc65de8e4e7f52534fb52b0f3ed04746ae267519eef2a83941e8085068b"

+[[package]]
+name = "atty"
+version = "0.2.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d9b39be18770d11421cdb1b9947a45dd3f37e93092cbf377614828a319d5fee8"
+dependencies = [
+ "hermit-abi",
+ "libc",
+ "winapi",
+]
+
 [[package]]
 name = "base64ct"
 version = "1.0.0"
@ -93,6 +113,17 @@ version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"

+[[package]]
+name = "chacha20"
+version = "0.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fee7ad89dc1128635074c268ee661f90c3f7e83d9fd12910608c36b47d6c3412"
+dependencies = [
+ "cfg-if 1.0.0",
+ "cipher",
+ "cpufeatures",
+]
+
 [[package]]
 name = "cipher"
 version = "0.3.0"
@ -108,9 +139,13 @@ version = "2.33.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "37e58ac78573c40708d45522f0d80fa2f01cc4f9b4e2bf749807255454312002"
 dependencies = [
+ "ansi_term",
+ "atty",
 "bitflags",
+ "strsim",
 "textwrap",
 "unicode-width",
+ "vec_map",
 ]

 [[package]]
@ -157,6 +192,17 @@ dependencies = [
 "cipher",
 ]

+[[package]]
+name = "derivative"
+version = "2.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fcc3dd5e9e9c0b295d6e1e4d811fb6f157d5ffd784b8d202fc62eac8035a770b"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "digest"
 version = "0.9.0"
@ -173,9 +219,12 @@ dependencies = [
 "aes",
 "argon2",
 "blake3",
+ "chacha20",
 "clap",
+ "cpufeatures",
 "hkdf",
 "hmac",
+ "num_enum",
 "rand",
 "rpassword",
 "zeroize",
@ -202,6 +251,15 @@ dependencies = [
 "wasi",
 ]

+[[package]]
+name = "hermit-abi"
+version = "0.1.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "62b467343b94ba476dcb2500d242dadbb39557df889310ac77c5d99100aaac33"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "hkdf"
 version = "0.11.0"
@ -228,6 +286,28 @@ version = "0.2.97"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "12b8adadd720df158f4d70dfe7ccc6adb0472d7c55ca83445f6a5ab3e36f8fb6"

+[[package]]
+name = "num_enum"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "226b45a5c2ac4dd696ed30fa6b94b057ad909c7b7fc2e0d0808192bced894066"
+dependencies = [
+ "derivative",
+ "num_enum_derive",
+]
+
+[[package]]
+name = "num_enum_derive"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1c0fd9eba1d5db0994a239e09c1be402d35622277e35468ba891aa5e3188ce7e"
+dependencies = [
+ "proc-macro-crate",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "opaque-debug"
 version = "0.3.0"
@ -251,6 +331,33 @@ version = "0.2.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857"

+[[package]]
+name = "proc-macro-crate"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1d6ea3c4595b96363c13943497db34af4460fb474a95c43f4446ad341b8c9785"
+dependencies = [
+ "toml",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f0d8caf72986c1a598726adc988bb5984792ef84f5ee5aa50209145ee8077038"
+dependencies = [
+ "unicode-xid",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c3d0b9745dc2debf507c8422de05d7226cc1f0644216dfdfead988f9b1ab32a7"
+dependencies = [
+ "proc-macro2",
+]
+
 [[package]]
 name = "rand"
 version = "0.8.4"
@ -301,12 +408,35 @@ dependencies = [
 "winapi",
 ]

+[[package]]
+name = "serde"
+version = "1.0.126"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec7505abeacaec74ae4778d9d9328fe5a5d04253220a85c4ee022239fc996d03"
+
+[[package]]
+name = "strsim"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8ea5119cdb4c55b55d432abb513a0429384878c15dde60cc77b1c99de1a95a6a"
+
 [[package]]
 name = "subtle"
 version = "2.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1e81da0851ada1f3e9d4312c704aa4f8806f0f9d69faaf8df2f3464b4a9437c2"

+[[package]]
+name = "syn"
+version = "1.0.73"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f71489ff30030d2ae598524f61326b902466f72a0fb1a8564c001cc63425bcc7"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-xid",
+]
+
 [[package]]
 name = "textwrap"
 version = "0.11.0"
@ -316,6 +446,15 @@ dependencies = [
 "unicode-width",
 ]

+[[package]]
+name = "toml"
+version = "0.5.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a31142970826733df8241ef35dc040ef98c679ab14d7c3e54d827099b3acecaa"
+dependencies = [
+ "serde",
+]
+
 [[package]]
 name = "typenum"
 version = "1.13.0"
@ -328,6 +467,18 @@ version = "0.1.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9337591893a19b88d8d87f2cec1e73fad5cdfd10e5a6f349f498ad6ea2ffb1e3"

+[[package]]
+name = "unicode-xid"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8ccb82d61f80a663efe1f787a51b16b5a51e3314d6ac365b08639f52387b33f3"
+
+[[package]]
+name = "vec_map"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f1bddf1187be692e79c5ffeab891132dfb0f236ed36a43c7ed39f1165ee20191"
+
 [[package]]
 name = "version_check"
 version = "0.9.3"
--- a/Cargo.toml
+++ b/Cargo.toml
@ -15,9 +15,12 @@ codegen-units = 1
 opt-level = 3

 [dependencies]
-clap = { version = "2.33", default-features = false }
+clap = "2.33"
 rand = "0.8"
-aes = { version = "0.7", features = ["ctr", "armv8"] }
+num_enum = "0.5"
+cpufeatures = "0.1"
+aes = { version = "0.7", features = ["ctr"] }
+chacha20 = "0.7"
 hmac = "0.11"
 blake3 = "0.3"
 hkdf = "0.11"
--- a/README.md
+++ b/README.md
@ -5,7 +5,7 @@ Secure symmetric encryption from the command line

 ## Features

-* Fast: written in [rust](https://www.rust-lang.org), encrypts with [AES-256-CTR](https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Counter_(CTR))
+* Fast: written in [rust](https://www.rust-lang.org), encrypts with [AES-256-CTR](https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Counter_(CTR)) or [XChaCha20](https://en.wikipedia.org/wiki/Salsa20#XChaCha)
 * [HMAC](https://en.wikipedia.org/wiki/HMAC) ciphertext authentication
 * Password brute-force resistance with [Argon2](https://en.wikipedia.org/wiki/Argon2)
 * Encryption from STDIN/STDOUT or from files
@ -71,8 +71,9 @@ FLAGS:
    -V, --version          Prints version information

 OPTIONS:
-    -p, --password <password>          
+    -p, --password <password>          Password used to derive encryption keys
    -b, --block-size <blocksize>       Size of file chunk (in bytes) [default: 65536]
+    -c, --cipher <cipher>              Encryption cipher to use [possible values: aes, xchacha20]
    -m, --memory-cost <memory cost>    Argon2 memory cost (in kilobytes) [default: 4096]
    -t, --threads <threads>            Argon2 parallelism (between 1 and 255) [default: 4]
    -i, --iterations <iterations>      Argon2 time cost [default: 10]
@ -141,15 +142,16 @@ hmac.update(argon2_time_cost);
 hmac.update(argon2_memory_cost);
 hmac.update(argon2_parallelism);
 hmac.update(random_hkdf_salt);
-hmac.update(random_nonce); //16 bytes random nonce used in AES-CTR cipher
+hmac.update(cipher); //1-byte representation of the symmetric cipher used to encrypt (either AES-CTR or XChaCha20)
+hmac.update(random_nonce); //random nonce used for encryption (16 bytes for AES-CTR, 24 for XChaCha20)
 ```

 All this parameters are also written in plain text in the header of the doby output.

-Now, doby initializes an AES-CTR cipher with `encryption_key` and `random_nonce` and starts the actual encryption. It reads chunks from the plaintext (according to the `--block-size` parameter), encrypts them with the cipher and updates the HMAC with the ciphertext.
+Now, doby initializes a symmetric cipher with `encryption_key` and `random_nonce` (either AES-CTR or XChaCha20, based on the `--cipher` option) and starts the actual encryption. It reads chunks from the plaintext (according to the `--block-size` parameter), encrypts them with the cipher and updates the HMAC with the ciphertext.

 ```rust
-let cipher = Aes256Ctr::new(encryption_key, random_nonce);
+let cipher = Aes256Ctr::new(encryption_key, random_nonce); //example with AES-CTR
 let mut n = 1;
 let mut chunk: [u8; block_size] = [0; block_size];
 while n != 0 {
@ -185,7 +187,7 @@ let master_key: [u8; 32] = argon2id(
 Then, doby starts decryption.

 ```rust
-let cipher = Aes256Ctr::new(encryption_key, nonce_read_from_input);
+let cipher = XChaCha20::new(encryption_key, nonce_read_from_input); //example with XChaCha20
 let mut n = 1;
 let mut chunk: [u8; block_size] = [0; block_size];
 while n != 0 {
--- a/src/bin/aes-ni.rs
+++ b/src/bin/aes-ni.rs
@ -0,0 +1,9 @@
+cpufeatures::new!(aes_ni, "aes");
+
+fn main() {
+    println!("AES-NI is {}supported on this device.", if aes_ni::get() {
+        ""
+    } else {
+        "NOT "
+    });
+}
--- a/src/bin/blocksize.rs
+++ b/src/bin/blocksize.rs
@ -6,7 +6,7 @@ use std::{
 };
 use doby::{
    encrypt, decrypt,
-    crypto::{ArgonParams, EncryptionParams, Cipher}
+    crypto::{ArgonParams, EncryptionParams, CipherAlgorithm, DobyCipher}
 };

 const MAX_BLOCK_SIZE: usize = 1_073_741_824; //1GB
@ -37,7 +37,7 @@ fn main() -> io::Result<()> {
        t_cost: 1,
        m_cost: 8,
        parallelism: 1,
-    });
+    }, CipherAlgorithm::AesCtr);

    let mut best_encrypt_time = None;
    let mut best_encrypt_block_size = None;
@ -49,7 +49,7 @@ fn main() -> io::Result<()> {
        let mut reader = BufReader::with_capacity(block_size, &input);
        let mut writer = BufWriter::with_capacity(block_size, &output);

-        let cipher = Cipher::new(PASSWORD, &params).unwrap();
+        let cipher = DobyCipher::new(PASSWORD, &params).unwrap();
        let t_encrypt = Instant::now();
        encrypt(&mut reader, &mut writer, &params, cipher, block_size, None)?;
        writer.flush()?;
@ -59,7 +59,7 @@ fn main() -> io::Result<()> {
        reset(&mut reader)?;
        reset(&mut writer)?;

-        let cipher = Cipher::new(PASSWORD, &params).unwrap();
+        let cipher = DobyCipher::new(PASSWORD, &params).unwrap();
        let t_decrypt = Instant::now();
        decrypt(&mut reader, &mut writer, cipher, block_size)?;
        writer.flush()?;
--- a/src/cli.rs
+++ b/src/cli.rs
@ -4,13 +4,16 @@ use std::{
    str::FromStr,
    io::{stdin, stdout, Read, Write},
 };
-use clap::{crate_name, crate_version, App, Arg};
-use crate::crypto::ArgonParams;
+use clap::{crate_name, crate_version, App, Arg, AppSettings};
+use crate::crypto::{ArgonParams, CipherAlgorithm};
+
+cpufeatures::new!(aes_ni, "aes");

 pub struct CliArgs {
    pub password: String,
    pub force_encrypt: bool,
    pub argon2_params: ArgonParams,
+    pub cipher: CipherAlgorithm,
    pub block_size: usize,
    pub reader: Box<dyn Read>,
    pub writer: Box<dyn Write>,
@ -19,6 +22,7 @@ pub struct CliArgs {
 pub fn parse() -> Option<CliArgs> {
    let app = App::new(crate_name!())
        .version(crate_version!())
+        .setting(AppSettings::ColoredHelp)
        .arg(Arg::with_name("INPUT").help("<PATH> | \"-\" or empty for stdin"))
        .arg(Arg::with_name("OUTPUT").help("<PATH> | \"-\" or empty for stdout"))
        .arg(
@ -32,6 +36,7 @@ pub fn parse() -> Option<CliArgs> {
                .short("p")
                .long("password")
                .value_name("password")
+                .help("Password used to derive encryption keys")
        )
        .arg(
            Arg::with_name("t_cost")
@ -64,6 +69,16 @@ pub fn parse() -> Option<CliArgs> {
                .help("Size of file chunk (in bytes)")
                .default_value("65536")
        )
+        .arg(
+            Arg::with_name("cipher")
+                .short("c")
+                .long("cipher")
+                .value_name("cipher")
+                .help("Encryption cipher to use")
+                .long_help("Encryption cipher to use. By default, AES is selected if AES-NI is supported. Otherwise, XChaCha20 is used.")
+                .possible_values(&["aes", "xchacha20"])
+                .case_insensitive(true)
+        )
        .get_matches();

    let params = {
@ -78,6 +93,21 @@ pub fn parse() -> Option<CliArgs> {
        }
    };

+    let cipher = app
+        .value_of("cipher")
+        .and_then(|s| Some(if s.to_lowercase() == "aes" {
+                CipherAlgorithm::AesCtr
+            } else {
+                CipherAlgorithm::XChaCha20
+            })
+        )
+        .unwrap_or_else(|| if aes_ni::get() {
+                CipherAlgorithm::AesCtr
+            } else {
+                CipherAlgorithm::XChaCha20
+            }
+        );
+
    let block_size = number(app.value_of("blocksize").unwrap())?;

    let input = app
@ -97,7 +127,7 @@ pub fn parse() -> Option<CliArgs> {
                Some(Box::new(File::create(s).unwrap()) as Box<dyn Write>)
            }
        })
-        .unwrap_or_else(|| Some(Box::new(stdout())));
+        .unwrap_or_else(|| Some(Box::new(stdout())))?;

    let password = match app.value_of("password") {
        Some(s) => s.to_string(),
@ -108,9 +138,10 @@ pub fn parse() -> Option<CliArgs> {
        password,
        force_encrypt: app.is_present("force-encrypt"),
        argon2_params: params,
+        cipher,
        block_size,
        reader: input,
-        writer: output?,
+        writer: output,
    })
 }

--- a/src/crypto.rs
+++ b/src/crypto.rs
@ -1,4 +1,6 @@
-use std::io::{self, Read, Write};
+use std::{convert::TryFrom, io::{self, Read, Write}};
+use num_enum::TryFromPrimitive;
+use chacha20::XChaCha20;
 use aes::{Aes256Ctr, cipher::{NewCipher, StreamCipher}};
 use hmac::{Hmac, Mac, NewMac};
 use rand::{Rng, rngs::OsRng};
@ -7,7 +9,8 @@ use hkdf::Hkdf;
 use zeroize::Zeroize;

 const SALT_LEN: usize = 64;
-const NONCE_LEN: usize = 16;
+const AES_NONCE_LEN: usize = 16;
+const XCHACHA20_NONCE_LEN: usize = 24;
 const HASH_LEN: usize = 32;
 const KEY_LEN: usize = HASH_LEN;

@ -17,28 +20,48 @@ pub struct ArgonParams {
    pub parallelism: u8,
 }

+#[derive(Clone, Copy, Debug, TryFromPrimitive)]
+#[repr(u8)]
+pub enum CipherAlgorithm {
+    AesCtr = 0,
+    XChaCha20 = 1,
+}
+
+impl CipherAlgorithm {
+    fn get_nonce_size(&self) -> usize {
+        match self {
+            CipherAlgorithm::AesCtr => AES_NONCE_LEN,
+            CipherAlgorithm::XChaCha20 => XCHACHA20_NONCE_LEN,
+        }
+    }
+}
+
 pub struct EncryptionParams {
    password_salt: [u8; SALT_LEN],
    argon2: ArgonParams,
    hkdf_salt: [u8; SALT_LEN],
-    nonce: [u8; NONCE_LEN],
+    nonce: Vec<u8>,
+    cipher: CipherAlgorithm,
 }

 impl EncryptionParams {
-    const PARAMS_LEN: usize = SALT_LEN*2 + 4*2 + 1 + NONCE_LEN;
+    fn get_params_len(&self) -> usize {
+        SALT_LEN*2 + 4*2 + 1 + self.cipher.get_nonce_size()
+    }

-    pub fn new(argon2_params: ArgonParams) -> EncryptionParams {
+    pub fn new(argon2_params: ArgonParams, cipher: CipherAlgorithm) -> EncryptionParams {
        let mut password_salt = [0; SALT_LEN];
        OsRng.fill(&mut password_salt);
        let mut hkdf_salt = [0; SALT_LEN];
        OsRng.fill(&mut hkdf_salt); 
-        let mut nonce = [0; NONCE_LEN];
-        OsRng.fill(&mut nonce);
+        let mut nonce = vec![0; cipher.get_nonce_size()];
+        OsRng.fill(&mut nonce[..]);
        EncryptionParams {
            password_salt,
            argon2: argon2_params,
            hkdf_salt,
            nonce,
+            cipher,
        }
    }
    pub fn write<W: Write>(&self, writer: &mut W) -> io::Result<()> {
@ -47,45 +70,54 @@ impl EncryptionParams {
        writer.write_all(&self.argon2.m_cost.to_be_bytes())?;
        writer.write_all(&self.argon2.parallelism.to_be_bytes())?;
        writer.write_all(&self.hkdf_salt)?;
+        writer.write_all(&(self.cipher as u8).to_be_bytes())?;
        writer.write_all(&self.nonce)?;
        Ok(())
    }
-    pub fn read<R: Read>(reader: &mut R) -> io::Result<Self> {
+    pub fn read<R: Read>(reader: &mut R) -> io::Result<Option<Self>> {
        let mut password_salt = [0; SALT_LEN];
        reader.read_exact(&mut password_salt)?;
-        let mut t_cost_buf = [0; 4];
-        reader.read_exact(&mut t_cost_buf)?;
-        let mut m_cost_buf = [0; 4];
-        reader.read_exact(&mut m_cost_buf)?;
-        let mut parallelism_buf = [0; 1];
-        reader.read_exact(&mut parallelism_buf)?;
+        let mut t_cost = [0; 4];
+        reader.read_exact(&mut t_cost)?;
+        let mut m_cost = [0; 4];
+        reader.read_exact(&mut m_cost)?;
+        let mut parallelism = [0; 1];
+        reader.read_exact(&mut parallelism)?;
        let mut hkdf_salt = [0; SALT_LEN];
        reader.read_exact(&mut hkdf_salt)?;
-        let mut nonce = [0; NONCE_LEN];
+        let mut cipher_buff = [0; 1];
+        reader.read_exact(&mut cipher_buff)?;
+        match CipherAlgorithm::try_from(cipher_buff[0]) {
+            Ok(cipher) => {
+                let mut nonce = vec![0; cipher.get_nonce_size()];
                reader.read_exact(&mut nonce)?;

                let argon2_params = ArgonParams {
-            t_cost: u32::from_be_bytes(t_cost_buf),
-            m_cost: u32::from_be_bytes(m_cost_buf),
-            parallelism: u8::from_be_bytes(parallelism_buf),
+                    t_cost: u32::from_be_bytes(t_cost),
+                    m_cost: u32::from_be_bytes(m_cost),
+                    parallelism: u8::from_be_bytes(parallelism),
                };

-        Ok(EncryptionParams {
+                Ok(Some(EncryptionParams {
                    password_salt,
                    argon2: argon2_params,
                    hkdf_salt,
                    nonce,
-        })
+                    cipher,
+                }))
+            }
+            Err(_) => Ok(None)
+        }
    }
 }

-pub struct Cipher {
-    cipher: Aes256Ctr,
+pub struct DobyCipher {
+    cipher: Box<dyn StreamCipher>,
    hmac: Hmac<blake3::Hasher>,
    buffer: Vec<u8>,
 }

-impl Cipher {
+impl DobyCipher {
    pub fn new(password: &[u8], params: &EncryptionParams) -> Result<Self, argon2::Error> {

        let argon = Argon2::new(None, params.argon2.t_cost, params.argon2.m_cost, params.argon2.parallelism.into(), Version::V0x13)?;
@ -99,13 +131,16 @@ impl Cipher {
        hkdf.expand(b"doby_authentication_key", &mut authentication_key).unwrap();
        master_key.zeroize();

-        let mut encoded_params = Vec::with_capacity(EncryptionParams::PARAMS_LEN);
+        let mut encoded_params = Vec::with_capacity(params.get_params_len());
        params.write(&mut encoded_params).unwrap();
        let mut hmac = Hmac::new_from_slice(&authentication_key).unwrap();
        hmac.update(&encoded_params);

-        Ok(Cipher {
-            cipher: Aes256Ctr::new_from_slices(&encryption_key, &params.nonce).unwrap(),
+        Ok(Self {
+            cipher: match params.cipher {
+                CipherAlgorithm::AesCtr => Box::new(Aes256Ctr::new_from_slices(&encryption_key, &params.nonce).unwrap()),
+                CipherAlgorithm::XChaCha20 => Box::new(XChaCha20::new_from_slices(&encryption_key, &params.nonce).unwrap()),
+            },
            hmac,
            buffer: Vec::new(),
        })
@ -127,8 +162,8 @@ impl Cipher {
        buff[..buffer_len].clone_from_slice(&self.buffer);
        let read = reader.read(&mut buff[buffer_len..])?;

-        self.buffer.clear();
        let n = if buffer_len + read >= HASH_LEN {
+            self.buffer.clear();
            buffer_len + read - HASH_LEN
        } else {
            0
--- a/src/lib.rs
+++ b/src/lib.rs
@ -2,11 +2,11 @@ pub mod cli;
 pub mod crypto;

 use std::io::{self, Read, Write};
-use crypto::{Cipher, EncryptionParams};
+use crypto::{DobyCipher, EncryptionParams};

 pub const MAGIC_BYTES: &[u8; 4] = b"DOBY";

-pub fn encrypt<R: Read, W: Write>(reader: &mut R, writer: &mut W, params: &EncryptionParams, mut cipher: Cipher, block_size: usize, already_read: Option<Vec<u8>>) -> io::Result<()> {
+pub fn encrypt<R: Read, W: Write>(reader: &mut R, writer: &mut W, params: &EncryptionParams, mut cipher: DobyCipher, block_size: usize, already_read: Option<Vec<u8>>) -> io::Result<()> {
    writer.write_all(MAGIC_BYTES)?;
    params.write(writer)?;
    let mut buff = vec![0; block_size];
@ -30,7 +30,7 @@ pub fn encrypt<R: Read, W: Write>(reader: &mut R, writer: &mut W, params: &Encry
    Ok(())
 }

-pub fn decrypt<R: Read, W: Write>(reader: &mut R, writer: &mut W, mut cipher: Cipher, block_size: usize) -> io::Result<bool> {
+pub fn decrypt<R: Read, W: Write>(reader: &mut R, writer: &mut W, mut cipher: DobyCipher, block_size: usize) -> io::Result<bool> {
    let mut buff = vec![0; block_size];
    loop {
        let n = cipher.decrypt_chunk(reader, &mut buff)?;
--- a/src/main.rs
+++ b/src/main.rs
@ -2,7 +2,7 @@ use std::io::{BufWriter, BufReader, Read};
 use zeroize::Zeroize;
 use doby::{
    cli,
-    crypto::{EncryptionParams, Cipher},
+    crypto::{EncryptionParams, DobyCipher},
    MAGIC_BYTES,
    decrypt,
    encrypt,
@ -22,7 +22,9 @@ fn main() {
                if magic_bytes == MAGIC_BYTES && !cli_args.force_encrypt { //we probably want to decrypt
                    match EncryptionParams::read(&mut reader) {
                        Ok(params) => {
-                            match Cipher::new(cli_args.password.as_bytes(), &params) {
+                            match params {
+                                Some(params) => {
+                                    match DobyCipher::new(cli_args.password.as_bytes(), &params) {
                                        Ok(cipher) => {
                                            match decrypt(&mut reader, &mut writer, cipher, cli_args.block_size) {
                                                Ok(verified) => {
@ -36,11 +38,14 @@ fn main() {
                                        Err(e) => eprintln!("Invalid argon2 params: {}", e)
                                    }
                                }
+                                None => eprintln!("Invalid cipher")
+                            }
+                        }
                        Err(e) => eprintln!("I/O error while reading headers: {}", e)
                    }
                } else { //otherwise, encrypt
-                    let params = EncryptionParams::new(cli_args.argon2_params);
-                    match Cipher::new(cli_args.password.as_bytes(), &params) {
+                    let params = EncryptionParams::new(cli_args.argon2_params, cli_args.cipher);
+                    match DobyCipher::new(cli_args.password.as_bytes(), &params) {
                        Ok(cipher) => {
                            if let Err(e) = encrypt(
                                &mut reader,