diff --git a/Cargo.toml b/Cargo.toml
index fa51688..e61d3b7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,3 +10,4 @@ publish = false
 [dependencies]
 anyhow = { version = "1.0.71", default-features = false, features = ["std"] }
 clap = { version = "4.3.11", default-features = false, features = ["derive", "std"] }
+data-encoding = { version = "2.4.0", default-features = false, features = ["std"] }
diff --git a/src/address.rs b/src/address.rs
new file mode 100644
index 0000000..47b06a3
--- /dev/null
+++ b/src/address.rs
@@ -0,0 +1,249 @@
+use anyhow::{ensure, Error, Result};
+use data_encoding::{BASE32_NOPAD, BASE64};
+use std::hash::{Hash, Hasher};
+use std::str::FromStr;
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct CodedAddress {
+	local_part: String,
+	sub_addr: String,
+	code: Vec<u8>,
+	domain: Option<String>,
+}
+
+impl FromStr for CodedAddress {
+	type Err = Error;
+
+	fn from_str(s: &str) -> Result<Self> {
+		let (local_part, domain) = split_local_part(s);
+		let parts: Vec<&str> = local_part.split(crate::DEFAULT_SEPARATOR).collect();
+		ensure!(parts.len() == 3, "{s}: invalid number of parts");
+		let local_part = parts[0].to_string();
+		let sub_addr = parts[1].to_string();
+		let code = BASE32_NOPAD.decode(parts[2].to_uppercase().as_bytes())?;
+		Ok(Self {
+			local_part,
+			sub_addr,
+			code,
+			domain,
+		})
+	}
+}
+
+#[derive(Clone, Debug)]
+pub struct KeyedAddress {
+	local_part: String,
+	domain: Option<String>,
+	key: Vec<u8>,
+}
+
+impl KeyedAddress {
+	pub fn check_code(&self, addr: &CodedAddress) -> bool {
+		// TODO
+		false
+	}
+}
+
+impl PartialEq for KeyedAddress {
+	fn eq(&self, other: &Self) -> bool {
+		self.local_part == other.local_part && self.domain == other.domain
+	}
+}
+
+impl PartialEq<CodedAddress> for KeyedAddress {
+	fn eq(&self, other: &CodedAddress) -> bool {
+		self.local_part == other.local_part && self.domain == other.domain
+	}
+}
+
+impl Eq for KeyedAddress {}
+
+impl Hash for KeyedAddress {
+	fn hash<H: Hasher>(&self, state: &mut H) {
+		self.local_part.hash(state);
+		self.domain.hash(state);
+	}
+}
+
+impl FromStr for KeyedAddress {
+	type Err = Error;
+
+	fn from_str(s: &str) -> Result<Self> {
+		let ksplit = s.rsplit_once(crate::KEY_SEPARATOR);
+		ensure!(ksplit.is_some(), "{s}: key separator not found");
+		let (address, key_b64) = ksplit.unwrap();
+		let (local_part, domain) = split_local_part(address);
+		let key = BASE64.decode(key_b64.as_bytes())?;
+		ensure!(!key.is_empty(), "{s}: key cannot be empty");
+		Ok(Self {
+			local_part,
+			domain,
+			key,
+		})
+	}
+}
+
+fn split_local_part(s: &str) -> (String, Option<String>) {
+	match s.rsplit_once('@') {
+		Some((local_part, domain)) => (local_part.to_string(), Some(domain.to_string())),
+		None => (s.to_string(), None),
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::{CodedAddress, KeyedAddress};
+	use std::str::FromStr;
+
+	#[test]
+	fn parse_valid_coded_addr_with_domain() {
+		let addr_str = "a+test+orsxg5a@example.org";
+		let addr = CodedAddress::from_str(addr_str);
+		assert!(addr.is_ok(), "unable to parse {addr_str}: {addr:?}");
+		let addr = addr.unwrap();
+		assert_eq!(addr.local_part, "a");
+		assert_eq!(addr.sub_addr, "test");
+		assert_eq!(addr.code, b"test");
+		assert_eq!(addr.domain, Some("example.org".to_string()));
+	}
+
+	#[test]
+	fn parse_valid_coded_addr_without_domain() {
+		let addr_str = "local.part+test+orsxg5a";
+		let addr = CodedAddress::from_str(addr_str);
+		assert!(addr.is_ok(), "unable to parse {addr_str}: {addr:?}");
+		let addr = addr.unwrap();
+		assert_eq!(addr.local_part, "local.part");
+		assert_eq!(addr.domain, None);
+	}
+
+	#[test]
+	fn parse_valid_keyed_addr_with_domain() {
+		let addr_str = "a@example.org:11voiefK5PgCX5F1TTcuoQ==";
+		let addr = KeyedAddress::from_str(addr_str);
+		assert!(addr.is_ok(), "unable to parse {addr_str}: {addr:?}");
+		let addr = addr.unwrap();
+		assert_eq!(addr.local_part, "a");
+		assert_eq!(addr.domain, Some("example.org".to_string()));
+		assert_eq!(
+			addr.key,
+			vec![
+				0xd7, 0x5b, 0xe8, 0x89, 0xe7, 0xca, 0xe4, 0xf8, 0x02, 0x5f, 0x91, 0x75, 0x4d, 0x37,
+				0x2e, 0xa1
+			]
+		);
+	}
+
+	#[test]
+	fn parse_valid_keyed_addr_without_domain() {
+		let addr_str = "local.part:3d74YQqk";
+		let addr = KeyedAddress::from_str(addr_str);
+		assert!(addr.is_ok(), "unable to parse {addr_str}: {addr:?}");
+		let addr = addr.unwrap();
+		assert_eq!(addr.local_part, "local.part");
+		assert_eq!(addr.domain, None);
+		assert_eq!(addr.key, vec![0xdd, 0xde, 0xf8, 0x61, 0x0a, 0xa4]);
+	}
+
+	#[test]
+	fn keyed_addr_empty_address() {
+		let res = KeyedAddress::from_str("");
+		assert!(res.is_err());
+	}
+
+	#[test]
+	fn keyed_addr_empty_base64() {
+		let res = KeyedAddress::from_str("a:");
+		assert!(res.is_err());
+	}
+
+	#[test]
+	fn keyed_addr_invalid_base64() {
+		let res = KeyedAddress::from_str("a:uh2kv%j3");
+		assert!(res.is_err());
+	}
+
+	#[test]
+	fn cmp_coded_addr_with_domain_eq() {
+		let addr_1 = CodedAddress::from_str("test+test+orsxg5a@example.org").unwrap();
+		let addr_2 = CodedAddress::from_str("test+test+orsxg5a@example.org").unwrap();
+		assert_eq!(addr_1, addr_2);
+	}
+
+	#[test]
+	fn cmp_coded_addr_without_domain_eq() {
+		let addr_1 = CodedAddress::from_str("test+test+orsxg5a").unwrap();
+		let addr_2 = CodedAddress::from_str("test+test+orsxg5a").unwrap();
+		assert_eq!(addr_1, addr_2);
+	}
+
+	#[test]
+	fn cmp_coded_addr_with_domain_ne() {
+		let addr_1 = CodedAddress::from_str("test+test+orsxg5a@example.org").unwrap();
+		let addr_2 = CodedAddress::from_str("test2+test+orsxg5a@example.org").unwrap();
+		assert_ne!(addr_1, addr_2);
+	}
+
+	#[test]
+	fn cmp_coded_addr_without_domain_ne() {
+		let addr_1 = CodedAddress::from_str("test+test+orsxg5a").unwrap();
+		let addr_2 = CodedAddress::from_str("test2+test+orsxg5a").unwrap();
+		assert_ne!(addr_1, addr_2);
+	}
+
+	#[test]
+	fn cmp_keyed_addr_with_domain_eq() {
+		let addr_1 = KeyedAddress::from_str("test@example.org:3d74YQqk").unwrap();
+		let addr_2 = KeyedAddress::from_str("test@example.org:11voiefK5PgCX5F1TTcuoQ==").unwrap();
+		assert_eq!(addr_1, addr_2);
+	}
+
+	#[test]
+	fn cmp_keyed_addr_without_domain_eq() {
+		let addr_1 = KeyedAddress::from_str("test:3d74YQqk").unwrap();
+		let addr_2 = KeyedAddress::from_str("test:11voiefK5PgCX5F1TTcuoQ==").unwrap();
+		assert_eq!(addr_1, addr_2);
+	}
+
+	#[test]
+	fn cmp_keyed_addr_with_domain_ne() {
+		let addr_1 = KeyedAddress::from_str("test@example.org:3d74YQqk").unwrap();
+		let addr_2 = KeyedAddress::from_str("test2@example.org:3d74YQqk").unwrap();
+		assert_ne!(addr_1, addr_2);
+	}
+
+	#[test]
+	fn cmp_keyed_addr_without_domain_ne() {
+		let addr_1 = KeyedAddress::from_str("test:3d74YQqk").unwrap();
+		let addr_2 = KeyedAddress::from_str("test2:3d74YQqk").unwrap();
+		assert_ne!(addr_1, addr_2);
+	}
+
+	#[test]
+	fn cmp_addr_types_with_domain_eq() {
+		let addr_1 = KeyedAddress::from_str("test@example.org:3d74YQqk").unwrap();
+		let addr_2 = CodedAddress::from_str("test+test+orsxg5a@example.org").unwrap();
+		assert_eq!(addr_1, addr_2);
+	}
+
+	#[test]
+	fn cmp_addr_types_without_domain_eq() {
+		let addr_1 = KeyedAddress::from_str("test:3d74YQqk").unwrap();
+		let addr_2 = CodedAddress::from_str("test+test+orsxg5a").unwrap();
+		assert_eq!(addr_1, addr_2);
+	}
+
+	#[test]
+	fn cmp_addr_types_with_domain_ne() {
+		let addr_1 = KeyedAddress::from_str("test@example.org:3d74YQqk").unwrap();
+		let addr_2 = CodedAddress::from_str("test+test+orsxg5a@example.com").unwrap();
+		assert_ne!(addr_1, addr_2);
+	}
+
+	#[test]
+	fn cmp_addr_types_without_domain_ne() {
+		let addr_1 = KeyedAddress::from_str("test:3d74YQqk").unwrap();
+		let addr_2 = CodedAddress::from_str("test2+test+orsxg5a").unwrap();
+		assert_ne!(addr_1, addr_2);
+	}
+}
diff --git a/src/config.rs b/src/config.rs
index 0779566..7de7177 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -1,9 +1,11 @@
+use crate::address::KeyedAddress;
 use anyhow::Result;
 use clap::Parser;
 use std::collections::HashSet;
 use std::fs::File;
 use std::io::{BufRead, BufReader};
 use std::path::PathBuf;
+use std::str::FromStr;
 
 #[derive(Parser, Debug)]
 #[command(author, version, about, long_about = None)]
@@ -17,10 +19,10 @@ pub struct Config {
 }
 
 impl Config {
-	pub fn addresses(&self) -> Result<HashSet<String>> {
+	pub fn addresses(&self) -> Result<HashSet<KeyedAddress>> {
 		let mut addr_set = HashSet::new();
 		for addr in &self.address {
-			addr_set.insert(addr.to_string());
+			addr_set.insert(KeyedAddress::from_str(addr)?);
 		}
 		if let Some(path) = &self.address_file {
 			let f = File::open(path)?;
@@ -29,7 +31,7 @@ impl Config {
 				let line = line?;
 				let addr = line.trim();
 				if !addr.is_empty() && !addr.starts_with(crate::COMMENT_CHAR) {
-					addr_set.insert(addr.to_string());
+					addr_set.insert(KeyedAddress::from_str(addr)?);
 				}
 			}
 		}
diff --git a/src/main.rs b/src/main.rs
index 54082b3..40b70d5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,9 +1,11 @@
 use clap::Parser;
 
+mod address;
 mod config;
 
 const COMMENT_CHAR: char = '#';
 const DEFAULT_SEPARATOR: char = '+';
+const KEY_SEPARATOR: char = ':';
 
 fn main() {
 	let cfg = config::Config::parse();