diff --git a/config/examples/stm32wb-uart-flash-encryption.config b/config/examples/stm32wb-uart-flash-encryption.config
index bef5700f..4b130939 100644
--- a/config/examples/stm32wb-uart-flash-encryption.config
+++ b/config/examples/stm32wb-uart-flash-encryption.config
@@ -21,6 +21,7 @@ DUALBANK_SWAP?=0
 IMAGE_HEADER_SIZE?=256
 PKA?=0
 ENCRYPT=1
+ENCRYPT_WITH_CHACHA=1
 WOLFTPM?=0
 WOLFBOOT_PARTITION_SIZE?=0x20000
 WOLFBOOT_SECTOR_SIZE?=0x1000
diff --git a/include/encrypt.h b/include/encrypt.h
index 9967f3d7..0ce389cc 100644
--- a/include/encrypt.h
+++ b/include/encrypt.h
@@ -57,10 +57,10 @@ extern Aes aes_dec, aes_enc;
 #define crypto_init() aes_init()
 #define crypto_encrypt(eb,b,sz) wc_AesCtrEncrypt(&aes_enc, eb, b, sz)
 #define crypto_decrypt(db,b,sz) wc_AesCtrEncrypt(&aes_dec, db, b, sz)
-#define crypto_set_iv(n, iv) aes_set_iv(n, iv)
+#define crypto_set_iv(n,a) aes_set_iv(n, a)
 
 int aes_init(void);
-void aes_set_iv(uint8_t *nonce, uint32_t iv_ctr);
+void aes_set_iv(uint8_t *nonce, uint32_t address);
 #endif /* ENCRYPT_WITH_CHACHA */
 
 /* Internal read/write functions (not exported in the libwolfboot API) */
diff --git a/include/wolfboot/wolfboot.h b/include/wolfboot/wolfboot.h
index 2133b9ce..5f7f487d 100644
--- a/include/wolfboot/wolfboot.h
+++ b/include/wolfboot/wolfboot.h
@@ -131,7 +131,7 @@ int wolfBoot_dualboot_candidate(void);
 
 /* Hashing function configuration */
 #if defined(WOLFBOOT_HASH_SHA256)
-#   define WOLFBOOT_SHA_BLOCK_SIZE (16)
+#   define WOLFBOOT_SHA_BLOCK_SIZE (256)
 #   define WOLFBOOT_SHA_HDR HDR_SHA256
 #   define WOLFBOOT_SHA_DIGEST_SIZE (32)
 #   define image_hash image_sha256
@@ -148,15 +148,17 @@ int wolfBoot_dualboot_candidate(void);
 
 
 #ifdef EXT_ENCRYPTED
-#define ENCRYPT_BLOCK_SIZE 16 
 /* Encryption support */
 #if defined(ENCRYPT_WITH_CHACHA)
+    #define ENCRYPT_BLOCK_SIZE 64
     #define ENCRYPT_KEY_SIZE 32 /* Chacha20 - 256bit */
     #define ENCRYPT_NONCE_SIZE 12 /* 96 bit*/
 #elif defined(ENCRYPT_WITH_AES128)
+    #define ENCRYPT_BLOCK_SIZE 16
     #define ENCRYPT_KEY_SIZE 16 /* AES128  */
     #define ENCRYPT_NONCE_SIZE 16 /* AES IV size */
 #elif defined(ENCRYPT_WITH_AES256)
+    #define ENCRYPT_BLOCK_SIZE 16
     #define ENCRYPT_KEY_SIZE 32 /* AES256 */
     #define ENCRYPT_NONCE_SIZE 16 /* AES IV size */
 #else
diff --git a/src/libwolfboot.c b/src/libwolfboot.c
index f2351ca3..adf7c35b 100644
--- a/src/libwolfboot.c
+++ b/src/libwolfboot.c
@@ -871,7 +871,6 @@ static inline uint8_t part_address(uintptr_t a)
 
 int ext_flash_encrypt_write(uintptr_t address, const uint8_t *data, int len)
 {
-    uint32_t iv_counter;
     uint8_t block[ENCRYPT_BLOCK_SIZE];
     uint8_t part;
     int sz = len;
@@ -913,12 +912,10 @@ int ext_flash_encrypt_write(uintptr_t address, const uint8_t *data, int len)
         address += step;
         data += step;
         sz -= step;
-        iv_counter++;
     }
     for (i = 0; i < sz / ENCRYPT_BLOCK_SIZE; i++) {
         XMEMCPY(block, data + (ENCRYPT_BLOCK_SIZE * i), ENCRYPT_BLOCK_SIZE);
         crypto_encrypt(ENCRYPT_CACHE + (ENCRYPT_BLOCK_SIZE * i), block, ENCRYPT_BLOCK_SIZE);
-        iv_counter++;
     }
     return ext_flash_write(address, ENCRYPT_CACHE, len);
 }
diff --git a/tools/keytools/sign.py b/tools/keytools/sign.py
index f3016b0c..3739e7bb 100755
--- a/tools/keytools/sign.py
+++ b/tools/keytools/sign.py
@@ -548,13 +548,12 @@ if (encrypt):
         key = ekeyfile.read(32)
         iv_nonce = ekeyfile.read(12)
         cha = ciphers.ChaCha(key, 32)
+        cha.set_iv(iv_nonce, 0)
         while True:
-            cha.set_iv(iv_nonce, off)
             buf = outfile.read(16)
             if len(buf) == 0:
                 break
             enc_outfile.write(cha.encrypt(buf))
-            off += 1
     elif aes128:
         key = ekeyfile.read(16)
         iv = ekeyfile.read(16)