diff --git a/includes/ft_ssl.h b/includes/ft_ssl.h
index a2afb62..dc1fc32 100644
--- a/includes/ft_ssl.h
+++ b/includes/ft_ssl.h
@@ -15,5 +15,6 @@ struct ssl_config
 };
 
 enum cli_code	cli_parse_arguments(int argc, char **argv, struct ssl_config *config);
+int				ssl_run(const struct ssl_config *config);
 
 #endif
diff --git a/includes/internal/ssl/ssl.h b/includes/internal/ssl/ssl.h
new file mode 100644
index 0000000..d5b4722
--- /dev/null
+++ b/includes/internal/ssl/ssl.h
@@ -0,0 +1,19 @@
+#ifndef FT_SSL_SSL_H
+#define FT_SSL_SSL_H
+
+#include <stdint.h>
+
+#include "ft_ssl.h"
+
+#define MAX_DIGEST_SIZE	64
+#define READ_BUFSIZE	4096
+
+int		run_string(const struct ssl_config *config);
+int		run_file(const struct ssl_config *config, const char *path);
+int		run_stdin(const struct ssl_config *config);
+int		digest_stream(const struct ssl_config *config, int fd,
+		const char *label, int show_algo, int echo);
+void	print_digest(const struct ssl_config *config, const uint8_t *digest,
+				const char *label, int show_algo);
+
+#endif
diff --git a/src/Makefile.am b/src/Makefile.am
index 3ee173d..2d348e3 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -41,6 +41,12 @@ FORCE:
 
 ft_ssl_SOURCES				= \
 							  main.c \
+							  ssl_run.c \
+							  ssl/run_stdin.c \
+							  ssl/run_string.c \
+							  ssl/run_file.c \
+							  ssl/digest.c \
+							  ssl/output.c \
 							  cli/parse.c \
 							  cli/handlers/option_map.c \
 							  cli/handlers/handle_help.c \
diff --git a/src/main.c b/src/main.c
index 42f8be3..502588f 100644
--- a/src/main.c
+++ b/src/main.c
@@ -17,10 +17,7 @@ main(int argc, char **argv)
 	ret = cli_parse_arguments(argc, argv, &config);
 	if (CLI_SUCCESS != ret)
 		goto cleanup;
-
-	/* TODO:
-	 * ret = ssl_run(&config);
-	 */
+	ret = ssl_run(&config);
 
 cleanup:
 	return (CLI_ERROR == ret) ? 2 : EXIT_SUCCESS;
diff --git a/src/ssl/digest.c b/src/ssl/digest.c
new file mode 100644
index 0000000..0065bce
--- /dev/null
+++ b/src/ssl/digest.c
@@ -0,0 +1,40 @@
+#include <unistd.h>
+
+#include <cli.h>
+#include <libft_ssl.h>
+
+#include "ft_ssl.h"
+#include "internal/ssl/ssl.h"
+
+/* Forward declarations */
+static void	process_chunk(const struct ssl_config *config, union digest_ctx *ctx,
+		const uint8_t *buf, size_t n, int echo);
+/* ------------------- */
+
+int
+digest_stream(const struct ssl_config *config, int fd,
+		const char *label, int show_algo, int echo)
+{
+	union digest_ctx	ctx;
+	uint8_t				buf[READ_BUFSIZE];
+	uint8_t				digest[MAX_DIGEST_SIZE];
+	ssize_t				n;
+
+	config->algo->init(&ctx);
+	while (0 < (n = read(fd, buf, sizeof(buf))))
+		process_chunk(config, &ctx, buf, (size_t)n, echo);
+	if (0 > n)
+		return CLI_ERROR;
+	config->algo->final(&ctx, digest);
+	print_digest(config, digest, label, show_algo);
+	return CLI_SUCCESS;
+}
+
+static void
+process_chunk(const struct ssl_config *config, union digest_ctx *ctx,
+		const uint8_t *buf, size_t n, int echo)
+{
+	if (echo)
+		(void)write(STDOUT_FILENO, buf, n);
+	config->algo->update(ctx, buf, n);
+}
diff --git a/src/ssl/output.c b/src/ssl/output.c
new file mode 100644
index 0000000..bf04b8f
--- /dev/null
+++ b/src/ssl/output.c
@@ -0,0 +1,109 @@
+#include <ctype.h>
+#include <stdio.h>
+
+#include <libft_ssl.h>
+
+#include "compiler.h"
+#include "ft_ssl.h"
+#include "ft_ssl_flags.h"
+#include "internal/ssl/ssl.h"
+
+enum fmt_mode
+{
+	FMT_STDIN,
+	FMT_DEFAULT,
+	FMT_QUIET,
+	FMT_REVERSE,
+};
+
+typedef void (*t_formatter)(const char *hex, const char *name_upper,
+		const char *label);
+
+/* Forward declarations */
+static enum fmt_mode	resolve_fmt(const struct ssl_config *config,
+		int show_algo);
+static void				build_hex(char *buf, const uint8_t *digest, size_t size);
+static void				build_upper(char *buf, const char *src, size_t size);
+static inline void		fmt_stdin(const char *hex, const char *name_upper,
+		const char *label);
+static inline void		fmt_default(const char *hex, const char *name_upper,
+		const char *label);
+static inline void		fmt_quiet(const char *hex, const char *name_upper,
+		const char *label);
+static inline void		fmt_reverse(const char *hex, const char *name_upper,
+		const char *label);
+/* ------------------- */
+
+static const t_formatter	s_formatters[] = {
+	[FMT_STDIN]		= fmt_stdin,
+	[FMT_DEFAULT]	= fmt_default,
+	[FMT_QUIET]		= fmt_quiet,
+	[FMT_REVERSE]	= fmt_reverse,
+};
+
+void
+print_digest(const struct ssl_config *config, const uint8_t *digest,
+		const char *label, int show_algo)
+{
+	char	hex[MAX_DIGEST_SIZE * 2 + 1];
+	char	name_upper[32];
+
+	build_hex(hex, digest, config->algo->digest_size);
+	build_upper(name_upper, config->algo->name, sizeof(name_upper));
+	s_formatters[resolve_fmt(config, show_algo)](hex, name_upper, label);
+}
+
+static enum fmt_mode
+resolve_fmt(const struct ssl_config *config, int show_algo)
+{
+	if (HAS_FLAG(config->flags, FLAG_Q))
+		return FMT_QUIET;
+	if (HAS_FLAG(config->flags, FLAG_R))
+		return FMT_REVERSE;
+	return show_algo ? FMT_DEFAULT : FMT_STDIN;
+}
+
+static void
+build_hex(char *buf, const uint8_t *digest, size_t size)
+{
+	size_t	i;
+
+	for (i = 0; i < size; i++)
+		(void)snprintf(buf + i * 2, 3, "%02x", (unsigned int)digest[i]);
+}
+
+static void
+build_upper(char *buf, const char *src, size_t size)
+{
+	size_t	i;
+
+	for (i = 0; i + 1 < size && '\0' != src[i]; i++)
+		buf[i] = (char)toupper((unsigned char)src[i]);
+	buf[i] = '\0';
+}
+
+static inline void
+fmt_stdin(const char *hex, __unused const char *name_upper, const char *label)
+{
+	printf("(%s)= %s\n", label, hex);
+}
+
+static inline void
+fmt_default(const char *hex, const char *name_upper, const char *label)
+{
+	printf("%s (%s) = %s\n", name_upper, label, hex);
+}
+
+static inline void
+fmt_quiet(const char *hex, __unused const char *name_upper,
+		__unused const char *label)
+{
+	printf("%s\n", hex);
+}
+
+static inline void
+fmt_reverse(const char *hex, __unused const char *name_upper,
+		const char *label)
+{
+	printf("%s %s\n", hex, label);
+}
diff --git a/src/ssl/run_file.c b/src/ssl/run_file.c
new file mode 100644
index 0000000..6227d75
--- /dev/null
+++ b/src/ssl/run_file.c
@@ -0,0 +1,28 @@
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <cli.h>
+
+#include "ft_ssl.h"
+#include "internal/ssl/ssl.h"
+#include "version_gen.h"
+
+int
+run_file(const struct ssl_config *config, const char *path)
+{
+	int	fd;
+	int	ret;
+
+	fd = open(path, O_RDONLY);
+	if (0 > fd)
+	{
+		fprintf(stderr, "%s: %s: %s\n", g_prog_name, path, strerror(errno));
+		return CLI_ERROR;
+	}
+	ret = digest_stream(config, fd, path, 1, 0);
+	close(fd);
+	return ret;
+}
diff --git a/src/ssl/run_stdin.c b/src/ssl/run_stdin.c
new file mode 100644
index 0000000..d2ba904
--- /dev/null
+++ b/src/ssl/run_stdin.c
@@ -0,0 +1,15 @@
+#include <unistd.h>
+
+#include <cli.h>
+
+#include "compiler.h"
+#include "ft_ssl.h"
+#include "ft_ssl_flags.h"
+#include "internal/ssl/ssl.h"
+
+int
+run_stdin(const struct ssl_config *config)
+{
+	return digest_stream(config, STDIN_FILENO, "stdin", 0,
+			HAS_FLAG(config->flags, FLAG_P));
+}
diff --git a/src/ssl/run_string.c b/src/ssl/run_string.c
new file mode 100644
index 0000000..bc1e7bd
--- /dev/null
+++ b/src/ssl/run_string.c
@@ -0,0 +1,24 @@
+#include <stdio.h>
+#include <string.h>
+
+#include <cli.h>
+#include <libft_ssl.h>
+
+#include "ft_ssl.h"
+#include "internal/ssl/ssl.h"
+
+int
+run_string(const struct ssl_config *config)
+{
+	union digest_ctx	ctx;
+	uint8_t				digest[MAX_DIGEST_SIZE];
+	char				label[4096];
+
+	config->algo->init(&ctx);
+	config->algo->update(&ctx, (const uint8_t *)config->string,
+			strlen(config->string));
+	config->algo->final(&ctx, digest);
+	(void)snprintf(label, sizeof(label), "\"%s\"", config->string);
+	print_digest(config, digest, label, 1);
+	return CLI_SUCCESS;
+}
diff --git a/src/ssl_run.c b/src/ssl_run.c
new file mode 100644
index 0000000..d63d507
--- /dev/null
+++ b/src/ssl_run.c
@@ -0,0 +1,56 @@
+#include <stdio.h>
+
+#include <cli.h>
+#include <libft_ssl.h>
+
+#include "compiler.h"
+#include "ft_ssl.h"
+#include "ft_ssl_flags.h"
+#include "internal/ssl/ssl.h"
+#include "version_gen.h"
+
+/* Forward declarations */
+static int			check_algo(const struct ssl_config *config);
+static inline void	update_ret(int *ret, int result);
+/* ------------------- */
+
+int
+ssl_run(const struct ssl_config *config)
+{
+	int	ret;
+	int	has_input;
+	int	i;
+
+	if (CLI_SUCCESS != check_algo(config))
+		return CLI_ERROR;
+	ret       = CLI_SUCCESS;
+	has_input = (NULL != config->string || 0 < config->nb_files);
+	if (HAS_FLAG(config->flags, FLAG_P) || !has_input)
+		update_ret(&ret, run_stdin(config));
+	if (NULL != config->string)
+		update_ret(&ret, run_string(config));
+	for (i = 0; i < config->nb_files; i++)
+		update_ret(&ret, run_file(config, config->files[i]));
+	return ret;
+}
+
+static int
+check_algo(const struct ssl_config *config)
+{
+	if (NULL == config->algo->init
+		|| NULL == config->algo->update
+		|| NULL == config->algo->final)
+	{
+		fprintf(stderr, "%s: %s: not yet implemented\n",
+				g_prog_name, config->algo->name);
+		return CLI_ERROR;
+	}
+	return CLI_SUCCESS;
+}
+
+static inline void
+update_ret(int *ret, int result)
+{
+	if (CLI_ERROR == result)
+		*ret = CLI_ERROR;
+}