diff --git a/Sha/sha1.cpp b/Sha/sha1.cpp
index 9ff3a1c..b707b44 100644
--- a/Sha/sha1.cpp
+++ b/Sha/sha1.cpp
@@ -8,7 +8,7 @@
 #define SHA1_K40 0x8f1bbcdc
 #define SHA1_K60 0xca62c1d6
 
-uint8_t sha1InitState[] PROGMEM = {
+const uint8_t sha1InitState[] PROGMEM = {
   0x01,0x23,0x45,0x67, // H0
   0x89,0xab,0xcd,0xef, // H1
   0xfe,0xdc,0xba,0x98, // H2
@@ -72,10 +72,18 @@ void Sha1Class::addUncounted(uint8_t data) {
   }
 }
 
-void Sha1Class::write(uint8_t data) {
+#if ARDUINO >= 100
+inline size_t Sha1Class::write(uint8_t data) {
   ++byteCount;
   addUncounted(data);
+  return 1;
 }
+#else
+inline void Sha1Class::write(uint8_t data) {
+  ++byteCount;
+  addUncounted(data);
+}
+#endif
 
 void Sha1Class::pad() {
   // Implement SHA-1 padding (fips180-2 §5.1.1)
diff --git a/Sha/sha1.h b/Sha/sha1.h
index 9975660..87b1a42 100644
--- a/Sha/sha1.h
+++ b/Sha/sha1.h
@@ -23,7 +23,11 @@ class Sha1Class : public Print
     void initHmac(const uint8_t* secret, int secretLength);
     uint8_t* result(void);
     uint8_t* resultHmac(void);
-    virtual void write(uint8_t);
+    #if ARDUINO >= 100
+		  virtual size_t write(uint8_t);
+	  #else
+  		virtual void write(uint8_t);
+  	#endif
     using Print::write;
   private:
     void pad();
diff --git a/Sha/sha256.cpp b/Sha/sha256.cpp
index e479d86..e8d22b3 100644
--- a/Sha/sha256.cpp
+++ b/Sha/sha256.cpp
@@ -3,7 +3,7 @@
 #include <avr/pgmspace.h>
 #include "sha256.h"
 
-uint32_t sha256K[] PROGMEM = {
+const uint32_t sha256K[] PROGMEM = {
   0x428a2f98,0x71374491,0xb5c0fbcf,0xe9b5dba5,0x3956c25b,0x59f111f1,0x923f82a4,0xab1c5ed5,
   0xd807aa98,0x12835b01,0x243185be,0x550c7dc3,0x72be5d74,0x80deb1fe,0x9bdc06a7,0xc19bf174,
   0xe49b69c1,0xefbe4786,0x0fc19dc6,0x240ca1cc,0x2de92c6f,0x4a7484aa,0x5cb0a9dc,0x76f988da,
@@ -16,7 +16,7 @@ uint32_t sha256K[] PROGMEM = {
 
 #define BUFFER_SIZE 64
 
-uint8_t sha256InitState[] PROGMEM = {
+const uint8_t sha256InitState[] PROGMEM = {
   0x67,0xe6,0x09,0x6a, // H0
   0x85,0xae,0x67,0xbb, // H1
   0x72,0xf3,0x6e,0x3c, // H2
@@ -87,10 +87,18 @@ void Sha256Class::addUncounted(uint8_t data) {
   }
 }
 
-void Sha256Class::write(uint8_t data) {
+#if ARDUINO >= 100
+inline size_t Sha256Class::write(uint8_t data) {
   ++byteCount;
   addUncounted(data);
+  return 1;
 }
+#else
+inline void Sha256Class::write(uint8_t data) {
+  ++byteCount;
+  addUncounted(data);
+}
+#endif
 
 void Sha256Class::pad() {
   // Implement SHA-256 padding (fips180-2 §5.1.1)
diff --git a/Sha/sha256.h b/Sha/sha256.h
index b4b5fd4..27b9636 100644
--- a/Sha/sha256.h
+++ b/Sha/sha256.h
@@ -23,7 +23,11 @@ class Sha256Class : public Print
     void initHmac(const uint8_t* secret, int secretLength);
     uint8_t* result(void);
     uint8_t* resultHmac(void);
-    virtual void write(uint8_t);
+    #if ARDUINO >= 100
+		  virtual size_t write(uint8_t);
+	  #else
+  		virtual void write(uint8_t);
+  	#endif
     using Print::write;
   private:
     void pad();