diff --git a/src/algorithm.rs b/src/algorithm.rs
new file mode 100644
index 0000000..d84fc1e
--- /dev/null
+++ b/src/algorithm.rs
@@ -0,0 +1,40 @@
+use std::str::FromStr;
+
+#[derive(Clone, Copy, Debug)]
+pub enum Algorithm {
+	Ed25519Sha256,
+	Rsa2048Sha256,
+	Rsa3072Sha256,
+	Rsa4096Sha256,
+}
+
+impl Default for Algorithm {
+	fn default() -> Self {
+		Self::Ed25519Sha256
+	}
+}
+
+impl ToString for Algorithm {
+	fn to_string(&self) -> String {
+		match self {
+			Self::Ed25519Sha256 => String::from("ed25519-sha256"),
+			Self::Rsa2048Sha256 => String::from("rsa2048-sha256"),
+			Self::Rsa3072Sha256 => String::from("rsa3072-sha256"),
+			Self::Rsa4096Sha256 => String::from("rsa4096-sha256"),
+		}
+	}
+}
+
+impl FromStr for Algorithm {
+	type Err = String;
+
+	fn from_str(s: &str) -> Result<Self, Self::Err> {
+		match s.to_lowercase().as_str() {
+			"ed25519-sha256" => Ok(Self::Ed25519Sha256),
+			"rsa2048-sha256" => Ok(Self::Rsa2048Sha256),
+			"rsa3072-sha256" => Ok(Self::Rsa3072Sha256),
+			"rsa4096-sha256" => Ok(Self::Rsa4096Sha256),
+			_ => Err(format!("{s}: invalid signing algorithm")),
+		}
+	}
+}
diff --git a/src/config.rs b/src/config.rs
index 7098bbf..492dbcc 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -1,3 +1,4 @@
+use crate::algorithm::Algorithm;
 use crate::canonicalization::Canonicalization;
 use clap::Parser;
 use std::collections::HashSet;
@@ -9,6 +10,8 @@ use std::path::PathBuf;
 #[derive(Parser, Debug)]
 #[command(author, version, about, long_about = None)]
 pub struct Config {
+	#[arg(short, long, default_value_t = Algorithm::default())]
+	algorithm: Algorithm,
 	#[arg(short, long, default_value_t = Canonicalization::default())]
 	canonicalization: Canonicalization,
 	#[arg(short, long)]
@@ -37,6 +40,10 @@ impl Config {
 		Ok(cnf)
 	}
 
+	pub fn algorithm(&self) -> Algorithm {
+		self.algorithm
+	}
+
 	pub fn canonicalization(&self) -> Canonicalization {
 		self.canonicalization
 	}
diff --git a/src/main.rs b/src/main.rs
index cdb75a3..7418565 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,4 @@
+mod algorithm;
 mod canonicalization;
 mod config;
 mod entry;