diff --git a/Makefile b/Makefile
index 92396f5..010dbfd 100644
--- a/Makefile
+++ b/Makefile
@@ -51,6 +51,7 @@ ENABLE_MESSENGER                        := 1
 ENABLE_MESSENGER_DELIVERY_NOTIFICATION  := 1
 ENABLE_MESSENGER_NOTIFICATION           := 1
 ENABLE_MESSENGER_UART                   := 0
+ENABLE_ENCRYPTION                       := 1
 
 #############################################################
 
@@ -163,6 +164,9 @@ ifeq ($(ENABLE_MESSENGER),1)
 	OBJS += app/messenger.o
 	OBJS += ui/messenger.o
 endif
+ifeq ($(ENABLE_ENCRYPTION),1)
+	OBJS += external/chacha/chacha.o
+endif
 
 ifeq ($(OS), Windows_NT)
 	TOP := $(dir $(realpath $(lastword $(MAKEFILE_LIST))))
@@ -374,6 +378,9 @@ endif
 ifeq ($(ENABLE_MESSENGER_UART),1)
 	CFLAGS  += -DENABLE_MESSENGER_UART
 endif
+ifeq ($(ENABLE_ENCRYPTION),1)
+	CFLAGS  += -DENABLE_ENCRYPTION
+endif
 
 LDFLAGS =
 ifeq ($(ENABLE_CLANG),0)
diff --git a/app/messenger.c b/app/messenger.c
index 35fef30..37eb44a 100644
--- a/app/messenger.c
+++ b/app/messenger.c
@@ -15,6 +15,9 @@
 #include "driver/system.h"
 #include "app/messenger.h"
 #include "ui/ui.h"
+#ifdef ENABLE_ENCRYPTION
+	#include "external/chacha/chacha.h"
+#endif
 
 #if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
     #include "driver/uart.h"
diff --git a/external/chacha/chacha.c b/external/chacha/chacha.c
new file mode 100644
index 0000000..ac8451d
--- /dev/null
+++ b/external/chacha/chacha.c
@@ -0,0 +1,227 @@
+/*
+chacha-merged.c version 20080118
+D. J. Bernstein
+Public domain.
+*/
+
+#include "chacha.h"
+
+#define U8C(v) (v##U)
+#define U32C(v) (v##U)
+
+#define U8V(v) ((unsigned char)(v) & U8C(0xFF))
+#define U32V(v) ((uint32_t)(v) & U32C(0xFFFFFFFF))
+
+#define ROTL32(v, n) \
+  (U32V((v) << (n)) | ((v) >> (32 - (n))))
+
+#if (USE_UNALIGNED == 1)
+#define U8TO32_LITTLE(p) \
+    (*((uint32_t *)(p)))
+#define U32TO8_LITTLE(p, v) \
+    do { \
+      *((uint32_t *)(p)) = v; \
+    } while (0)
+#else
+#define U8TO32_LITTLE(p) \
+  (((uint32_t)((p)[0])      ) | \
+   ((uint32_t)((p)[1]) <<  8) | \
+   ((uint32_t)((p)[2]) << 16) | \
+   ((uint32_t)((p)[3]) << 24))
+#define U32TO8_LITTLE(p, v) \
+  do { \
+    (p)[0] = U8V((v)      ); \
+    (p)[1] = U8V((v) >>  8); \
+    (p)[2] = U8V((v) >> 16); \
+    (p)[3] = U8V((v) >> 24); \
+  } while (0)
+#endif
+
+#define ROTATE(v,c) (ROTL32(v,c))
+#define XOR(v,w) ((v) ^ (w))
+#define PLUS(v,w) (U32V((v) + (w)))
+#define PLUSONE(v) (PLUS((v),1))
+
+#define QUARTERROUND(a,b,c,d) \
+  a = PLUS(a,b); d = ROTATE(XOR(d,a),16); \
+  c = PLUS(c,d); b = ROTATE(XOR(b,c),12); \
+  a = PLUS(a,b); d = ROTATE(XOR(d,a), 8); \
+  c = PLUS(c,d); b = ROTATE(XOR(b,c), 7);
+
+static const char sigma[16] = "expand 32-byte k";
+static const char tau[16] = "expand 16-byte k";
+
+void
+chacha_keysetup(struct chacha_ctx *x,const unsigned char *k,uint32_t kbits)
+{
+  const char *constants;
+
+  x->input[4] = U8TO32_LITTLE(k + 0);
+  x->input[5] = U8TO32_LITTLE(k + 4);
+  x->input[6] = U8TO32_LITTLE(k + 8);
+  x->input[7] = U8TO32_LITTLE(k + 12);
+  if (kbits == 256) { /* recommended */
+    k += 16;
+    constants = sigma;
+  } else { /* kbits == 128 */
+    constants = tau;
+  }
+  x->input[8] = U8TO32_LITTLE(k + 0);
+  x->input[9] = U8TO32_LITTLE(k + 4);
+  x->input[10] = U8TO32_LITTLE(k + 8);
+  x->input[11] = U8TO32_LITTLE(k + 12);
+  x->input[0] = U8TO32_LITTLE(constants + 0);
+  x->input[1] = U8TO32_LITTLE(constants + 4);
+  x->input[2] = U8TO32_LITTLE(constants + 8);
+  x->input[3] = U8TO32_LITTLE(constants + 12);
+}
+
+void
+chacha_ivsetup(struct chacha_ctx *x, const unsigned char *iv, const unsigned char *counter)
+{
+  x->input[12] = counter == NULL ? 0 : U8TO32_LITTLE(counter + 0);
+  //x->input[13] = counter == NULL ? 0 : U8TO32_LITTLE(counter + 4);
+  x->input[13] = U8TO32_LITTLE(iv + 0);
+  x->input[14] = U8TO32_LITTLE(iv + 4);
+  x->input[15] = U8TO32_LITTLE(iv + 8);
+}
+
+void
+chacha_encrypt_bytes(struct chacha_ctx *x,const unsigned char *m,unsigned char *c,uint32_t bytes)
+{
+  uint32_t x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;
+  uint32_t j0, j1, j2, j3, j4, j5, j6, j7, j8, j9, j10, j11, j12, j13, j14, j15;
+  unsigned char *ctarget = NULL;
+  unsigned char tmp[64];
+  u_int8_t i;
+
+  if (!bytes) return;
+
+  j0 = x->input[0];
+  j1 = x->input[1];
+  j2 = x->input[2];
+  j3 = x->input[3];
+  j4 = x->input[4];
+  j5 = x->input[5];
+  j6 = x->input[6];
+  j7 = x->input[7];
+  j8 = x->input[8];
+  j9 = x->input[9];
+  j10 = x->input[10];
+  j11 = x->input[11];
+  j12 = x->input[12];
+  j13 = x->input[13];
+  j14 = x->input[14];
+  j15 = x->input[15];
+
+  for (;;) {
+    if (bytes < 64) {
+#if (USE_MEMCPY == 1)
+      memcpy(tmp, m, bytes);
+#else
+      for (i = 0;i < bytes;++i) tmp[i] = m[i];
+#endif
+      m = tmp;
+      ctarget = c;
+      c = tmp;
+    }
+    x0 = j0;
+    x1 = j1;
+    x2 = j2;
+    x3 = j3;
+    x4 = j4;
+    x5 = j5;
+    x6 = j6;
+    x7 = j7;
+    x8 = j8;
+    x9 = j9;
+    x10 = j10;
+    x11 = j11;
+    x12 = j12;
+    x13 = j13;
+    x14 = j14;
+    x15 = j15;
+    for (i = 20;i > 0;i -= 2) {
+      QUARTERROUND( x0, x4, x8,x12)
+      QUARTERROUND( x1, x5, x9,x13)
+      QUARTERROUND( x2, x6,x10,x14)
+      QUARTERROUND( x3, x7,x11,x15)
+      QUARTERROUND( x0, x5,x10,x15)
+      QUARTERROUND( x1, x6,x11,x12)
+      QUARTERROUND( x2, x7, x8,x13)
+      QUARTERROUND( x3, x4, x9,x14)
+    }
+    x0 = PLUS(x0,j0);
+    x1 = PLUS(x1,j1);
+    x2 = PLUS(x2,j2);
+    x3 = PLUS(x3,j3);
+    x4 = PLUS(x4,j4);
+    x5 = PLUS(x5,j5);
+    x6 = PLUS(x6,j6);
+    x7 = PLUS(x7,j7);
+    x8 = PLUS(x8,j8);
+    x9 = PLUS(x9,j9);
+    x10 = PLUS(x10,j10);
+    x11 = PLUS(x11,j11);
+    x12 = PLUS(x12,j12);
+    x13 = PLUS(x13,j13);
+    x14 = PLUS(x14,j14);
+    x15 = PLUS(x15,j15);
+
+    x0 = XOR(x0,U8TO32_LITTLE(m + 0));
+    x1 = XOR(x1,U8TO32_LITTLE(m + 4));
+    x2 = XOR(x2,U8TO32_LITTLE(m + 8));
+    x3 = XOR(x3,U8TO32_LITTLE(m + 12));
+    x4 = XOR(x4,U8TO32_LITTLE(m + 16));
+    x5 = XOR(x5,U8TO32_LITTLE(m + 20));
+    x6 = XOR(x6,U8TO32_LITTLE(m + 24));
+    x7 = XOR(x7,U8TO32_LITTLE(m + 28));
+    x8 = XOR(x8,U8TO32_LITTLE(m + 32));
+    x9 = XOR(x9,U8TO32_LITTLE(m + 36));
+    x10 = XOR(x10,U8TO32_LITTLE(m + 40));
+    x11 = XOR(x11,U8TO32_LITTLE(m + 44));
+    x12 = XOR(x12,U8TO32_LITTLE(m + 48));
+    x13 = XOR(x13,U8TO32_LITTLE(m + 52));
+    x14 = XOR(x14,U8TO32_LITTLE(m + 56));
+    x15 = XOR(x15,U8TO32_LITTLE(m + 60));
+
+    j12 = PLUSONE(j12);
+    if (!j12) {
+      j13 = PLUSONE(j13);
+      /* stopping at 2^70 bytes per nonce is user's responsibility */
+    }
+
+    U32TO8_LITTLE(c + 0,x0);
+    U32TO8_LITTLE(c + 4,x1);
+    U32TO8_LITTLE(c + 8,x2);
+    U32TO8_LITTLE(c + 12,x3);
+    U32TO8_LITTLE(c + 16,x4);
+    U32TO8_LITTLE(c + 20,x5);
+    U32TO8_LITTLE(c + 24,x6);
+    U32TO8_LITTLE(c + 28,x7);
+    U32TO8_LITTLE(c + 32,x8);
+    U32TO8_LITTLE(c + 36,x9);
+    U32TO8_LITTLE(c + 40,x10);
+    U32TO8_LITTLE(c + 44,x11);
+    U32TO8_LITTLE(c + 48,x12);
+    U32TO8_LITTLE(c + 52,x13);
+    U32TO8_LITTLE(c + 56,x14);
+    U32TO8_LITTLE(c + 60,x15);
+
+    if (bytes <= 64) {
+      if (bytes < 64) {
+#if (USE_MEMCPY == 1)
+        memcpy(ctarget, c, bytes);
+#else
+        for (i = 0;i < bytes;++i) ctarget[i] = c[i];
+#endif
+      }
+      x->input[12] = j12;
+      x->input[13] = j13;
+      return;
+    }
+    bytes -= 64;
+    c += 64;
+    m += 64;
+  }
+}
diff --git a/external/chacha/chacha.h b/external/chacha/chacha.h
new file mode 100644
index 0000000..3892001
--- /dev/null
+++ b/external/chacha/chacha.h
@@ -0,0 +1,38 @@
+/*
+chacha-merged.c version 20080118
+D. J. Bernstein
+Public domain.
+*/
+
+#ifndef CHACHA_H
+#define CHACHA_H
+
+#include <sys/types.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define CHACHA_MINKEYLEN	16
+#define CHACHA_NONCELEN		8
+#define CHACHA_CTRLEN		8
+#define CHACHA_STATELEN		(CHACHA_NONCELEN+CHACHA_CTRLEN)
+#define CHACHA_BLOCKLEN		64
+
+/* use memcpy() to copy blocks of memory (typically faster) */
+#define USE_MEMCPY          1
+/* use unaligned little-endian load/store (can be faster) */
+#define USE_UNALIGNED       0
+
+struct chacha_ctx {
+	uint32_t input[16];
+};
+
+void chacha_keysetup(struct chacha_ctx *x, const unsigned char *k,
+        uint32_t kbits);
+void chacha_ivsetup(struct chacha_ctx *x, const unsigned char *iv,
+        const unsigned char *ctr);
+void chacha_encrypt_bytes(struct chacha_ctx *x, const unsigned char *m,
+        unsigned char *c, uint32_t bytes);
+
+#endif	/* CHACHA_H */
+