diff --git a/Makefile b/Makefile
index 84bcd16..c3dc6c4 100644
--- a/Makefile
+++ b/Makefile
@@ -12,7 +12,7 @@ OBJ_DIR := obj
 SRCs := $(wildcard $(SRC_DIR)/*.c)
 OBJs := $(SRCs:$(SRC_DIR)/%.c=$(OBJ_DIR)/%.o)
 
-CFLAGS = --std=c99 -D_POSIX_C_SOURCE=200112L -O3 -Wall -Werror -Wextra -pedantic
+CFLAGS = --std=c99 -D_POSIX_C_SOURCE=200809L -O3 -Wall -Werror -Wextra -pedantic
 CFLAGS += -flto
 LDFLAGS += -lportaudio -lopus -lsodium
 
diff --git a/src/addrbook.c b/src/addrbook.c
new file mode 100644
index 0000000..197a311
--- /dev/null
+++ b/src/addrbook.c
@@ -0,0 +1,112 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "addrbook.h"
+#include "crypt.h"
+
+#define ADDRBOOK_DELIM_COUNT 4
+
+char *addrbook_entry_to_string(const addrbook_entry_t *const ent) {
+    size_t str_len = CRYPT_PKEY_HEXLEN + ent->name_len + ent->last_addr_len
+        + ent->last_port_len + ADDRBOOK_DELIM_COUNT;
+    char *str = (char *)malloc(str_len * sizeof(char));
+    sprintf(str, "%.128s\t%.*s\t%.*s\t%.*s\n", ent->pubk, ent->name_len, ent->name,
+        ent->last_addr_len, ent->last_addr, ent->last_port_len, ent->last_port);
+    return str;
+}
+
+int addrbook_entry_from_string(addrbook_entry_t *const ent, char * str) {
+    char *tok = strtok(str, "\t\n");
+    if (tok == NULL)
+        return -1;
+    memcpy(ent->pubk, tok, CRYPT_PKEY_HEXLEN);
+
+    tok = strtok(NULL, "\t\n");
+    ent->name = strdup(tok);
+    ent->name_len = strlen(ent->name);
+
+    tok = strtok(NULL, "\t\n");
+    ent->last_addr = strdup(tok);
+    ent->last_addr_len = strlen(ent->last_addr);
+
+    tok = strtok(NULL, "\t\n");
+    ent->last_port = strdup(tok);
+    ent->last_port_len = strlen(ent->last_port);
+
+    return 0;
+}
+
+int addrbook_init(addrbook_t *const ab) {
+    ab->entries = (addrbook_entry_t *)malloc(sizeof(addrbook_entry_t));
+    if (ab->entries == NULL)
+        return -1;
+    ab->entries_len = 0;
+    return 0;
+}
+
+void addrbook_destroy(addrbook_t *const ab) {
+    free(ab->entries);
+    ab->entries_len = 0;
+}
+
+int addrbook_load(addrbook_t *ab, FILE *in) {
+    char *line = NULL;
+    size_t line_len = 0;
+    size_t lines = 0;
+
+    while (getline(&line, &line_len, in) != -1)
+        ++lines;
+
+    if (ab->entries != NULL)
+        free(ab->entries);
+    ab->entries = (addrbook_entry_t *)malloc(lines * sizeof(addrbook_entry_t));
+    if (ab->entries == NULL)
+            return -1;
+    ab->entries_len = 0;
+
+    fseek(in, 0, SEEK_SET);
+
+    addrbook_entry_t ent;
+
+    while (getline(&line, &line_len, in) != -1) {
+        if (addrbook_entry_from_string(&ent, line) == -1) {
+            addrbook_destroy(ab);
+            return -1;
+        }
+
+        if (addrbook_add(ab, &ent) == -1) {
+            addrbook_destroy(ab);
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+int addrbook_store(addrbook_t *ab, FILE *out) {
+    for (size_t i = 0; i < ab->entries_len; ++i) {
+        char *ent_str = addrbook_entry_to_string(&ab->entries[i]);
+        fputs(ent_str, out);
+        free(ent_str);
+    }
+    return 0;
+}
+
+int addrbook_add(addrbook_t *const ab, const addrbook_entry_t *const ent) {
+    if (addrbook_get(ab, ent->pubk) != NULL)
+        return -1;
+    if (ab->entries_len > 0)
+        ab->entries = realloc(ab->entries, ++ab->entries_len);
+    else
+        ++ab->entries_len;
+    ab->entries[ab->entries_len-1] = *ent;
+    return 0;
+}
+
+addrbook_entry_t *addrbook_get(const addrbook_t *const ab, const char pkey[CRYPT_PKEY_HEXLEN]) {
+    for (size_t i = 0; i < ab->entries_len; ++i)
+        if (strncmp(ab->entries[i].pubk, pkey, CRYPT_PKEY_HEXLEN) == 0)
+            return &ab->entries[i];
+    return NULL;
+}
diff --git a/src/addrbook.h b/src/addrbook.h
new file mode 100644
index 0000000..44568bf
--- /dev/null
+++ b/src/addrbook.h
@@ -0,0 +1,37 @@
+#ifndef _ADDRBOOK_H_
+#define _ADDRBOOK_H_
+
+#include "crypt.h"
+#include <netinet/in.h>
+
+#define ADDRBOOK_NAME_MAXLEN 64
+#define ADDRBOOK_PORT_MAXLEN 5
+
+typedef struct addrbook_entry_t {
+    char pubk[CRYPT_PKEY_HEXLEN];
+    char *name;
+    char *last_addr;
+    char *last_port;
+    unsigned char name_len;
+    unsigned char last_addr_len;
+    unsigned char last_port_len;
+} addrbook_entry_t;
+
+char *addrbook_entry_to_string(const addrbook_entry_t *const ent);
+int addrbook_entry_from_string(addrbook_entry_t *const ent, char * str);
+
+typedef struct addrbook_t {
+    addrbook_entry_t *entries;
+    size_t entries_len;
+} addrbook_t;
+
+int addrbook_init(addrbook_t *const ab);
+void addrbook_destroy(addrbook_t *const ab);
+
+int addrbook_load(addrbook_t *ab, FILE *in);
+int addrbook_store(addrbook_t *ab, FILE *out);
+
+int addrbook_add(addrbook_t *const ab, const addrbook_entry_t *const ent);
+addrbook_entry_t *addrbook_get(const addrbook_t *const ab, const char pkey[CRYPT_PKEY_HEXLEN]);
+
+#endif /* _ADDRBOOK_H_ */
diff --git a/src/main.c b/src/main.c
index 7948cc2..76a8f02 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,6 +1,9 @@
 // #include "audio.h"
+#include "addrbook.h"
 #include "crypt.h"
 #include "net.h"
+#include <stdio.h>
+#include <string.h>
 
 #define CHANNELS 1
 #define SAMPLE_RATE 48000
@@ -17,6 +20,21 @@ void usage(void) {
 }
 
 int main(int argc, char **argv) {
+
+    addrbook_t ab = {0};
+
+    FILE *in = fopen("addressbook_key", "r");
+
+    addrbook_load(&ab, in);
+
+    for (size_t i = 0; i < ab.entries_len; ++i)
+        printf("%ld: %.128s %s %s %s\n", i, ab.entries[i].pubk, ab.entries[i].name, ab.entries[i].last_addr, ab.entries[i].last_port);
+
+    fclose(in);
+    addrbook_destroy(&ab);
+
+    return 0;
+
     if (argc < 4) {
         usage();
         return -1;
@@ -66,6 +84,7 @@ int main(int argc, char **argv) {
 
 cleanup:
 
+    addrbook_destroy(&ab);
     net_destroy(&n);
     crypt_session_destroy(&s);
     crypt_key_destroy(&ok);