diff --git a/src/ieu/aes_instructions/aes64e.sv b/src/ieu/aes_instructions/aes64e.sv
index 18f4e135e..98a18fa23 100644
--- a/src/ieu/aes_instructions/aes64e.sv
+++ b/src/ieu/aes_instructions/aes64e.sv
@@ -29,9 +29,11 @@ module aes64e(
     input  logic [63:0] rs1,
     input  logic [63:0] rs2,
     input  logic        finalround, 
+    input  logic [31:0] Sbox0Out,
+    output logic [31:0] SboxEIn,
     output logic [63:0] result
 );
-   
+  
     logic [127:0] ShiftRowOut;
     logic [63:0]  SboxOut, MixcolOut;
                 
@@ -39,8 +41,11 @@ module aes64e(
     aesshiftrow srow({rs2,rs1}, ShiftRowOut);
    
     // Apply substitution box to 2 lower words
-    aessboxword sbox0(ShiftRowOut[31:0],  SboxOut[31:0]);
-    aessboxword sbox1(ShiftRowOut[63:32], SboxOut[63:32]);
+    // Use the shared sbox in zknde64.sv for the first sbox
+    assign SboxEIn = ShiftRowOut[31:0];
+    assign SboxOut[31:0] = Sbox0Out;
+
+    aessboxword sbox1(ShiftRowOut[63:32], SboxOut[63:32]); // instantiate second sbox
 
     // Apply mix columns operations
     aesmixcolumns mw0(SboxOut[31:0],  MixcolOut[31:0]);
diff --git a/src/ieu/aes_instructions/aes64ks1i.sv b/src/ieu/aes_instructions/aes64ks1i.sv
index ac7d5849b..ef36e1cc6 100644
--- a/src/ieu/aes_instructions/aes64ks1i.sv
+++ b/src/ieu/aes_instructions/aes64ks1i.sv
@@ -28,20 +28,25 @@
 module aes64ks1i(
    input  logic [3:0]  round,
    input  logic [63:0] rs1,
+   input  logic [31:0] Sbox0Out,
+   output logic [31:0] SboxKIn,
    output logic [63:0] result
 );                 
                  
    logic 			        finalround;
    logic [7:0] 			  rcon8;
-   logic [31:0] 		     rcon, rs1Rotate, tmp2, SboxOut;
+   logic [31:0] 		     rcon, rs1Rotate;
    
    rconlut128 rc(round, rcon8);                           // Get rcon value from lookup table
    assign rcon = {24'b0, rcon8};                          // Zero-pad RCON 
    assign rs1Rotate = {rs1[39:32], rs1[63:40]};           // Get rotated value fo ruse in tmp2
    assign finalround = (round == 4'b1010);                // round 10 is the last one 
-   assign tmp2 = finalround ? rs1[63:32] : rs1Rotate;     // Don't rotate on the last round
-   aessboxword sbox(tmp2, SboxOut);                       // Substitute bytes of value obtained for tmp2 using Rijndael sbox
-   assign result[31:0] = SboxOut ^ rcon;
-   assign result[63:32] = SboxOut ^ rcon;	
+   assign SboxKIn = finalround ? rs1[63:32] : rs1Rotate;     // Don't rotate on the last round
+
+   // Share sbox with encryption in zknde64.  This module just sends value to shared sbox and gets result back
+   // send out value as SboxKIn, get back subsittuted result as Sbox0Out
+
+   assign result[31:0] = Sbox0Out ^ rcon;
+   assign result[63:32] = Sbox0Out ^ rcon;	
 endmodule
 
diff --git a/src/ieu/kmu/zknde64.sv b/src/ieu/kmu/zknde64.sv
index cae271f89..f4f79ddb4 100644
--- a/src/ieu/kmu/zknde64.sv
+++ b/src/ieu/kmu/zknde64.sv
@@ -35,14 +35,19 @@ module zknde64 import cvw::*; #(parameter cvw_t P) (
 );
    
     logic [63:0] 	     aes64dRes, aes64eRes, aes64ks1iRes, aes64ks2Res;
+    logic [31:0]         SboxEIn, SboxKIn, Sbox0In, Sbox0Out;
    
     if (P.ZKND_SUPPORTED) // ZKND supports aes64ds, aes64dsm, aes64im
         aes64d    aes64d(.rs1(A), .rs2(B), .finalround(ZKNSelect[2]), .aes64im(ZKNSelect[3]), .result(aes64dRes)); // decode AES
     if (P.ZKNE_SUPPORTED) // ZKNE supports aes64es, aes64esm
-        aes64e    aes64e(.rs1(A), .rs2(B), .finalround(ZKNSelect[2]), .result(aes64eRes));
+        aes64e    aes64e(.rs1(A), .rs2(B), .finalround(ZKNSelect[2]), .Sbox0Out, .SboxEIn, .result(aes64eRes));
+
+    // One S Box is always needed for aes64ks1i and is also needed for aes64e if that is supported.  Put it at the top level to allow sharing
+    mux2 #(32) sboxmux(SboxEIn, SboxKIn, ZKNSelect[1], Sbox0In);
+    aessboxword sbox(Sbox0In, Sbox0Out);                       // Substitute bytes of value obtained for tmp2 using Rijndael sbox
 
     // Both ZKND and ZKNE support aes64ks1i and aes64ks2 instructions
-    aes64ks1i aes64ks1i(.round, .rs1(A), .result(aes64ks1iRes));
+    aes64ks1i aes64ks1i(.round, .rs1(A), .Sbox0Out, .SboxKIn, .result(aes64ks1iRes));
     aes64ks2  aes64ks2(.rs2(B), .rs1(A), .result(aes64ks2Res));
    
     // Choose among decrypt, encrypt, key schedule 1, key schedule 2 results