diff --git a/firmware/arch/arm/include/biosincludes.h b/firmware/arch/arm/include/biosincludes.h
index b7feacb..2c08dee 100644
--- a/firmware/arch/arm/include/biosincludes.h
+++ b/firmware/arch/arm/include/biosincludes.h
@@ -34,6 +34,10 @@
 #define UINT64_RSHIFT(v, shiftby) (((uint64_t)(v)) >> (shiftby))
 #define UINT64_MULT32(v, multby)  (((uint64_t)(v)) * ((uint32_t)(multby)))
 
+#ifndef UINT32_MAX
+#define UINT32_MAX (UINT32_C(0xffffffffU))
+#endif
+
 #ifndef UINT64_MAX
 #define UINT64_MAX (UINT64_C(0xffffffffffffffffULL))
 #endif
diff --git a/firmware/lib/cryptolib/include/sha.h b/firmware/lib/cryptolib/include/sha.h
index 46e417d..8beb296 100644
--- a/firmware/lib/cryptolib/include/sha.h
+++ b/firmware/lib/cryptolib/include/sha.h
@@ -58,11 +58,11 @@
 uint8_t* SHA1_final(SHA1_CTX* ctx);
 
 void SHA256_init(SHA256_CTX* ctx);
-void SHA256_update(SHA256_CTX* ctx, const uint8_t* data, uint64_t len);
+void SHA256_update(SHA256_CTX* ctx, const uint8_t* data, uint32_t len);
 uint8_t* SHA256_final(SHA256_CTX* ctx);
 
 void SHA512_init(SHA512_CTX* ctx);
-void SHA512_update(SHA512_CTX* ctx, const uint8_t* data, uint64_t len);
+void SHA512_update(SHA512_CTX* ctx, const uint8_t* data, uint32_t len);
 uint8_t* SHA512_final(SHA512_CTX* ctx);
 
 /* Convenience function for SHA-1.  Computes hash on [data] of length [len].
diff --git a/firmware/lib/cryptolib/sha2.c b/firmware/lib/cryptolib/sha2.c
index aa26917..d8dce06 100644
--- a/firmware/lib/cryptolib/sha2.c
+++ b/firmware/lib/cryptolib/sha2.c
@@ -332,22 +332,22 @@
 
 
 
-void SHA256_update(SHA256_CTX* ctx, const uint8_t* data, uint64_t len) {
+void SHA256_update(SHA256_CTX* ctx, const uint8_t* data, uint32_t len) {
     unsigned int block_nb;
     unsigned int new_len, rem_len, tmp_len;
     const uint8_t *shifted_data;
 
     tmp_len = SHA256_BLOCK_SIZE - ctx->len;
-    rem_len = len < tmp_len ? (unsigned int)len : tmp_len;
+    rem_len = len < tmp_len ? len : tmp_len;
 
     Memcpy(&ctx->block[ctx->len], data, rem_len);
 
     if (ctx->len + len < SHA256_BLOCK_SIZE) {
-        ctx->len += (uint32_t)len;
+        ctx->len += len;
         return;
     }
 
-    new_len = (unsigned int)len - rem_len;
+    new_len = len - rem_len;
     block_nb = new_len / SHA256_BLOCK_SIZE;
 
     shifted_data = data + rem_len;
@@ -424,8 +424,7 @@
 
 
 static void SHA512_transform(SHA512_CTX* ctx, const uint8_t* message,
-                   unsigned int block_nb)
-{
+                             unsigned int block_nb) {
   uint64_t w[80];
   uint64_t wv[8];
   uint64_t t1, t2;
@@ -520,22 +519,22 @@
 
 
 void SHA512_update(SHA512_CTX* ctx, const uint8_t* data,
-                   uint64_t len) {
+                   uint32_t len) {
     unsigned int block_nb;
     unsigned int new_len, rem_len, tmp_len;
     const uint8_t* shifted_data;
 
     tmp_len = SHA512_BLOCK_SIZE - ctx->len;
-    rem_len = len < tmp_len ? (unsigned int)len : tmp_len;
+    rem_len = len < tmp_len ? len : tmp_len;
 
     Memcpy(&ctx->block[ctx->len], data, rem_len);
 
     if (ctx->len + len < SHA512_BLOCK_SIZE) {
-        ctx->len += (uint32_t)len;
+        ctx->len += len;
         return;
     }
 
-    new_len = (unsigned int)len - rem_len;
+    new_len = len - rem_len;
     block_nb = new_len / SHA512_BLOCK_SIZE;
 
     shifted_data = data + rem_len;
@@ -593,31 +592,60 @@
 }
 
 
-
-/* Convenient functions. */
 uint8_t* SHA256(const uint8_t* data, uint64_t len, uint8_t* digest) {
-  const uint8_t* p;
+  const uint8_t* input_ptr;
+  const uint8_t* result;
+  uint64_t remaining_len;
   int i;
   SHA256_CTX ctx;
+
   SHA256_init(&ctx);
-  SHA256_update(&ctx, data, len);
-  p = SHA256_final(&ctx);
+
+  input_ptr = data;
+  remaining_len = len;
+
+  /* Process data in at most UINT32_MAX byte chunks at a time. */
+  while (remaining_len) {
+    uint32_t block_size;
+    block_size = (uint32_t) ((remaining_len >= UINT32_MAX) ?
+                             UINT32_MAX : remaining_len);
+    SHA256_update(&ctx, input_ptr, block_size);
+    remaining_len -= block_size;
+    input_ptr += block_size;
+  }
+
+  result = SHA256_final(&ctx);
   for (i = 0; i < SHA256_DIGEST_SIZE; ++i) {
-    digest[i] = *p++;
+    digest[i] = *result++;
   }
   return digest;
 }
 
 
 uint8_t* SHA512(const uint8_t* data, uint64_t len, uint8_t* digest) {
-  const uint8_t* p;
+  const uint8_t* input_ptr;
+  const uint8_t* result;
+  uint64_t remaining_len;
   int i;
   SHA512_CTX ctx;
   SHA512_init(&ctx);
-  SHA512_update(&ctx, data, len);
-  p = SHA512_final(&ctx);
+
+  input_ptr = data;
+  remaining_len = len;
+
+  /* Process data in at most UINT32_MAX byte chunks at a time. */
+  while (remaining_len) {
+    uint32_t block_size;
+    block_size = (uint32_t) ((remaining_len >= UINT32_MAX) ?
+                             UINT32_MAX : remaining_len);
+       SHA512_update(&ctx, input_ptr, block_size);
+    remaining_len -= block_size;
+    input_ptr += block_size;
+  }
+
+  result = SHA512_final(&ctx);
   for (i = 0; i < SHA512_DIGEST_SIZE; ++i) {
-    digest[i] = *p++;
+    digest[i] = *result++;
   }
   return digest;
 }