diff --git a/auth-client.cc b/auth-client.cc
index cdf2872..9dc4a1b 100644
--- a/auth-client.cc
+++ b/auth-client.cc
@@ -1,13 +1,4 @@
-#include <fstream>
-#include <iostream>
-
 #include <getopt.h>
-#include <netdb.h>
-#include <netinet/in.h>
-#include <stdio.h>
-#include <string.h>
-#include <sys/types.h>
-#include <sys/socket.h>
 
 #include "crypto.h"
 
@@ -48,24 +39,10 @@ int main(int argc, char *argv[]) {
 	}
 
 	std::string secret_key;
-	{
-		std::fstream secret_key_file(secret_key_filename, std::fstream::in);
-		if (secret_key_file.fail()) {
-			std::cerr << "Failed to open secret key file" << std::endl;
-			return 1;
-		}
-		secret_key_file >> secret_key;
-	}
+	CryptoBase::ReadKeyFromFile(secret_key_filename, &secret_key);
 
 	std::string server_public_key;
-	{
-		std::fstream server_public_key_file(server_public_key_filename, std::fstream::in);
-		if (server_public_key_file.fail()) {
-			std::cerr << "Failed to open server public key file" << std::endl;
-			return 1;
-		}
-		server_public_key_file >> server_public_key;
-	}
+	CryptoBase::ReadKeyFromFile(server_public_key_filename, &server_public_key);
 
 	auto client = CryptoPubClient::FromHostname(server_address, server_port, secret_key, server_public_key);
 	client->Loop();
diff --git a/auth-server.cc b/auth-server.cc
index 8bdc090..96feb01 100644
--- a/auth-server.cc
+++ b/auth-server.cc
@@ -1,12 +1,4 @@
-#include <fstream>
-#include <iostream>
-
 #include <getopt.h>
-#include <netinet/in.h>
-#include <stdio.h>
-#include <string.h>
-#include <sys/types.h>
-#include <sys/socket.h>
 
 #include "crypto.h"
 
@@ -28,14 +20,7 @@ int main(int argc, char *argv[]) {
 	}
 
 	std::string secret_key;
-	{
-		std::fstream secret_key_file(secret_key_filename, std::fstream::in);
-		if (secret_key_file.fail()) {
-			std::cerr << "Failed to open secret key file" << std::endl;
-			return 1;
-		}
-		secret_key_file >> secret_key;
-	}
+	CryptoBase::ReadKeyFromFile(secret_key_filename, &secret_key);
 
 	CryptoPubServer server(secret_key);
 	server.Loop();
diff --git a/crypto.cc b/crypto.cc
index f9ecb1e..ce10e15 100644
--- a/crypto.cc
+++ b/crypto.cc
@@ -4,6 +4,7 @@
 #include <unistd.h>
 
 #include <cassert>
+#include <fstream>
 #include <iostream>
 
 #include <sodium/crypto_box.h>
@@ -46,6 +47,18 @@ void CryptoBase::DerivePublicKey(const std::string& secret_key, std::string* pub
 	public_key->assign((char*)buf, crypto_box_PUBLICKEYBYTES);
 }
 
+void CryptoBase::ReadKeyFromFile(const std::string& filename, std::string* key) {
+	std::fstream key_file(filename, std::fstream::in);
+	assert(!key_file.fail());
+	key_file >> *key;
+}
+
+void CryptoBase::WriteKeyToFile(const std::string& filename, const std::string& key) {
+	std::fstream key_file(filename, std::fstream::out);
+	assert(!key_file.fail());
+	key_file << key;
+}
+
 void CryptoBase::EncodeEncryptAppend(const std::string& secret_key, const std::string& public_key, const TLVNode& input, TLVNode* container) {
 	assert(secret_key.length() == crypto_box_SECRETKEYBYTES);
 	assert(public_key.length() == crypto_box_PUBLICKEYBYTES);
diff --git a/crypto.h b/crypto.h
index 5416356..7abe225 100644
--- a/crypto.h
+++ b/crypto.h
@@ -13,6 +13,9 @@ class CryptoBase {
 		static void GenKey(std::string* key);
 		static void GenKeyPair(std::string* secret_key, std::string* public_key);
 		static void DerivePublicKey(const std::string& secret_key, std::string* public_key);
+		static void ReadKeyFromFile(const std::string& filename, std::string* key);
+		static void WriteKeyToFile(const std::string& filename, const std::string& key);
+
 		static void EncodeEncryptAppend(const std::string& secret_key, const std::string& public_key, const TLVNode& input, TLVNode* container);
 		TLVNode *DecryptDecode(const std::string& secret_key, const std::string& public_key, const TLVNode& input);
 
diff --git a/gen-key.cc b/gen-key.cc
index 6cba2ff..ca38135 100644
--- a/gen-key.cc
+++ b/gen-key.cc
@@ -13,14 +13,7 @@ int main(int argc, char *argv[]) {
 	std::string key;
 	CryptoBase::GenKey(&key);
 
-	{
-		std::fstream key_file(argv[1], std::fstream::out);
-		if (key_file.fail()) {
-			std::cerr << "Failed to open key file" << std::endl;
-			return 1;
-		}
-		key_file << key;
-	}
+	CryptoBase::WriteKeyToFile(argv[1], key);
 
 	return 0;
 }
diff --git a/gen-keypair.cc b/gen-keypair.cc
index 2f45fa8..6fbce4d 100644
--- a/gen-keypair.cc
+++ b/gen-keypair.cc
@@ -13,23 +13,8 @@ int main(int argc, char *argv[]) {
 	std::string secret_key, public_key;
 	CryptoBase::GenKeyPair(&secret_key, &public_key);
 
-	{
-		std::fstream secret_key_file(argv[1], std::fstream::out);
-		if (secret_key_file.fail()) {
-			std::cerr << "Failed to open secret key file" << std::endl;
-			return 1;
-		}
-		secret_key_file << secret_key;
-	}
-
-	{
-		std::fstream public_key_file(argv[2], std::fstream::out);
-		if (public_key_file.fail()) {
-			std::cerr << "Failed to open public key file" << std::endl;
-			return 1;
-		}
-		public_key_file << public_key;
-	}
+	CryptoBase::WriteKeyToFile(argv[1], secret_key);
+	CryptoBase::WriteKeyToFile(argv[2], public_key);
 
 	return 0;
 }