diff --git a/sm3/kdf_mult4_asm.go b/sm3/kdf_mult4_asm.go
index d6c80687..07a188c6 100644
--- a/sm3/kdf_mult4_asm.go
+++ b/sm3/kdf_mult4_asm.go
@@ -65,7 +65,7 @@ func kdfBy4(baseMD *digest, keyLen int, limit int) []byte {
 	}
 
 	var ct uint32 = 1
-	k := make([]byte, keyLen)
+	k := make([]byte, limit*Size)
 	ret := k
 	times := limit / parallelSize4
 	for i := 0; i < times; i++ {
@@ -90,7 +90,7 @@ func kdfBy4(baseMD *digest, keyLen int, limit int) []byte {
 		ct++
 	}
 
-	return k
+	return k[:keyLen]
 }
 
 //go:noescape
diff --git a/sm3/kdf_mult8_amd64.go b/sm3/kdf_mult8_amd64.go
index 067a5141..07275a80 100644
--- a/sm3/kdf_mult8_amd64.go
+++ b/sm3/kdf_mult8_amd64.go
@@ -26,7 +26,7 @@ func kdfBy8(baseMD *digest, keyLen int, limit int) []byte {
 	len <<= 3
 
 	var ct uint32 = 1
-	k := make([]byte, keyLen)
+	k := make([]byte, limit * Size)
 	ret := k
 
 	// prepare temporary buffer
@@ -89,7 +89,7 @@ func kdfBy8(baseMD *digest, keyLen int, limit int) []byte {
 		ct++
 	}
 
-	return k
+	return k[:keyLen]
 }
 
 //go:noescape
diff --git a/sm3/sm3_test.go b/sm3/sm3_test.go
index 7b244c9a..8c80ea8d 100644
--- a/sm3/sm3_test.go
+++ b/sm3/sm3_test.go
@@ -419,11 +419,18 @@ func TestKdf(t *testing.T) {
 		{"sm3 case 2", args{[]byte("emmansun"), 32}, "708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd4"},
 		{"sm3 case 3", args{[]byte("emmansun"), 48}, "708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"},
 		{"sm3 case 4", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 48}, "49cf14649f324a07e0d5bb2a00f7f05d5f5bdd6d14dff028e071327ec031104590eddb18f98b763e18bf382ff7c3875f"},
-		{"sm3 case 5", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 128}, "49cf14649f324a07e0d5bb2a00f7f05d5f5bdd6d14dff028e071327ec031104590eddb18f98b763e18bf382ff7c3875f30277f3179baebd795e7853fa643fdf280d8d7b81a2ab7829f615e132ab376d32194cd315908d27090e1180ce442d9be99322523db5bfac40ac5acb03550f5c93e5b01b1d71f2630868909a6a1250edb"},
-		{"sm3 case 6", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 159}, "49cf14649f324a07e0d5bb2a00f7f05d5f5bdd6d14dff028e071327ec031104590eddb18f98b763e18bf382ff7c3875f30277f3179baebd795e7853fa643fdf280d8d7b81a2ab7829f615e132ab376d32194cd315908d27090e1180ce442d9be99322523db5bfac40ac5acb03550f5c93e5b01b1d71f2630868909a6a1250edb9abb2c6b0673e349f64c6577d4ba1b0a9c360016bae9478f8a80d5426327e8"},
-		{"sm3 case 7", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 300}, "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"},
-		{"sm3 case 8", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 416}, "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"},
-		{"sm3 case 9", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 516}, "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"},
+		{"sm3 case 5", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 121}, "49cf14649f324a07e0d5bb2a00f7f05d5f5bdd6d14dff028e071327ec031104590eddb18f98b763e18bf382ff7c3875f30277f3179baebd795e7853fa643fdf280d8d7b81a2ab7829f615e132ab376d32194cd315908d27090e1180ce442d9be99322523db5bfac40ac5acb03550f5c93e5b01b1d71f263086"},
+		{"sm3 case 6", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 128}, "49cf14649f324a07e0d5bb2a00f7f05d5f5bdd6d14dff028e071327ec031104590eddb18f98b763e18bf382ff7c3875f30277f3179baebd795e7853fa643fdf280d8d7b81a2ab7829f615e132ab376d32194cd315908d27090e1180ce442d9be99322523db5bfac40ac5acb03550f5c93e5b01b1d71f2630868909a6a1250edb"},
+		{"sm3 case 7", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 159}, "49cf14649f324a07e0d5bb2a00f7f05d5f5bdd6d14dff028e071327ec031104590eddb18f98b763e18bf382ff7c3875f30277f3179baebd795e7853fa643fdf280d8d7b81a2ab7829f615e132ab376d32194cd315908d27090e1180ce442d9be99322523db5bfac40ac5acb03550f5c93e5b01b1d71f2630868909a6a1250edb9abb2c6b0673e349f64c6577d4ba1b0a9c360016bae9478f8a80d5426327e8"},
+		{"sm3 case 8", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 250}, "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"},
+		{"sm3 case 9", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 256}, "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"},
+		{"sm3 case 10", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 257}, "49cf14649f324a07e0d5bb2a00f7f05d5f5bdd6d14dff028e071327ec031104590eddb18f98b763e18bf382ff7c3875f30277f3179baebd795e7853fa643fdf280d8d7b81a2ab7829f615e132ab376d32194cd315908d27090e1180ce442d9be99322523db5bfac40ac5acb03550f5c93e5b01b1d71f2630868909a6a1250edb9abb2c6b0673e349f64c6577d4ba1b0a9c360016bae9478f8a80d5426327e84ea915c10ef39a016618b00aaae8735a8a1405180746ddd7ccd05dc890c5e5d07f49c40afdbc09267859ac5967b8c1163dc6defab955604e45e349a51df11d81b298424b84472607249a05b481ae88d98a9273ecdee009add0619641bd7d9f0b13a5"},
+		{"sm3 case 11", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 300}, "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"},
+		{"sm3 case 12", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 383}, "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"},
+		{"sm3 case 13", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 384}, "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"},
+		{"sm3 case 14", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 385}, "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"},
+		{"sm3 case 15", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 416}, "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"},
+		{"sm3 case 16", args{[]byte("708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493708993ef1388a0ae4245a19bb6c02554c632633e356ddb989beb804fda96cfd47eba4fa460e7b277bc6b4ce4d07ed493"), 516}, "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"},
 	}
 	for _, tt := range tests {
 		wantBytes, _ := hex.DecodeString(tt.want)