OFB/CTR decryption is the same as encryption

2 files changed, 8 insertions, 73 deletions

diff --git a/include/aesni/aes.h b/include/aesni/aes.h
index b7a2854..bad5463 100644
--- a/include/aesni/aes.h
+++ b/include/aesni/aes.h
@@ -410,12 +410,7 @@ static __inline AesNI_Aes_Block __fastcall aesni_aes128_decrypt_block_ofb(
     AesNI_Aes_Block init_vector,
     AesNI_Aes_Block* next_init_vector)
 {
-    assert(encryption_keys);
-    assert(next_init_vector);
-
-    AesNI_Aes_Block tmp = aesni_aes128_encrypt_block_(init_vector, encryption_keys);
-    *next_init_vector = tmp;
-    return aesni_xor_block128(tmp, ciphertext);
+    return aesni_aes128_encrypt_block_ofb(ciphertext, encryption_keys, init_vector, next_init_vector);
 }
 
 /**
@@ -458,12 +453,7 @@ static __inline AesNI_Aes_Block __fastcall aesni_aes128_decrypt_block_ctr(
     AesNI_Aes_Block init_vector,
     AesNI_Aes_Block* next_init_vector)
 {
-    assert(encryption_keys);
-    assert(next_init_vector);
-
-    AesNI_Aes_Block plaintext = aesni_xor_block128(ciphertext, aesni_aes128_encrypt_block_(init_vector, encryption_keys));
-    *next_init_vector = aesni_aes_inc_counter(init_vector);
-    return plaintext;
+    return aesni_aes128_encrypt_block_ctr(ciphertext, encryption_keys, init_vector, next_init_vector);
 }
 
 /**
@@ -668,12 +658,7 @@ static __inline AesNI_Aes_Block __fastcall aesni_aes192_decrypt_block_ofb(
     AesNI_Aes_Block init_vector,
     AesNI_Aes_Block* next_init_vector)
 {
-    assert(encryption_keys);
-    assert(next_init_vector);
-
-    AesNI_Aes_Block tmp = aesni_aes192_encrypt_block_(init_vector, encryption_keys);
-    *next_init_vector = tmp;
-    return aesni_xor_block128(tmp, ciphertext);
+    return aesni_aes192_encrypt_block_ofb(ciphertext, encryption_keys, init_vector, next_init_vector);
 }
 
 /**
@@ -716,12 +701,7 @@ static __inline AesNI_Aes_Block __fastcall aesni_aes192_decrypt_block_ctr(
     AesNI_Aes_Block init_vector,
     AesNI_Aes_Block* next_init_vector)
 {
-    assert(encryption_keys);
-    assert(next_init_vector);
-
-    AesNI_Aes_Block plaintext = aesni_xor_block128(ciphertext, aesni_aes192_encrypt_block_(init_vector, encryption_keys));
-    *next_init_vector = aesni_aes_inc_counter(init_vector);
-    return plaintext;
+    return aesni_aes192_encrypt_block_ctr(ciphertext, encryption_keys, init_vector, next_init_vector);
 }
 
 /**
@@ -926,12 +906,7 @@ static __inline AesNI_Aes_Block __fastcall aesni_aes256_decrypt_block_ofb(
     AesNI_Aes_Block init_vector,
     AesNI_Aes_Block* next_init_vector)
 {
-    assert(encryption_keys);
-    assert(next_init_vector);
-
-    AesNI_Aes_Block tmp = aesni_aes256_encrypt_block_(init_vector, encryption_keys);
-    *next_init_vector = tmp;
-    return aesni_xor_block128(tmp, ciphertext);
+    return aesni_aes256_encrypt_block_ofb(ciphertext, encryption_keys, init_vector, next_init_vector);
 }
 
 /**
@@ -974,12 +949,7 @@ static __inline AesNI_Aes_Block __fastcall aesni_aes256_decrypt_block_ctr(
     AesNI_Aes_Block init_vector,
     AesNI_Aes_Block* next_init_vector)
 {
-    assert(encryption_keys);
-    assert(next_init_vector);
-
-    AesNI_Aes_Block plaintext = aesni_xor_block128(ciphertext, aesni_aes256_encrypt_block_(init_vector, encryption_keys));
-    *next_init_vector = aesni_aes_inc_counter(init_vector);
-    return plaintext;
+    return aesni_aes256_encrypt_block_ctr(ciphertext, encryption_keys, init_vector, next_init_vector);
 }
 
 #ifdef __cplusplus
diff --git a/src/box.c b/src/box.c
index c74100c..d10e963 100644
--- a/src/box.c
+++ b/src/box.c
@@ -234,41 +234,6 @@ static AesNI_StatusCode aesni_box_decrypt_cfb(
     return status;
 }
 
-static AesNI_StatusCode aesni_box_decrypt_ofb(
-    AesNI_Box* box,
-    const AesNI_BoxBlock* input,
-    AesNI_BoxBlock* output,
-    AesNI_ErrorDetails* err_details)
-{
-    AesNI_StatusCode status = box->algorithm_iface->encrypt(
-        &box->iv,
-        &box->encrypt_params,
-        output,
-        err_details);
-    if (aesni_is_error(status))
-        return status;
-
-    box->iv = *output;
-
-    status = box->algorithm_iface->xor_block(
-        output,
-        input,
-        err_details);
-    if (aesni_is_error(status))
-        return status;
-
-    return status;
-}
-
-static AesNI_StatusCode aesni_box_decrypt_ctr(
-    AesNI_Box* box,
-    const AesNI_BoxBlock* input,
-    AesNI_BoxBlock* output,
-    AesNI_ErrorDetails* err_details)
-{
-    return aesni_box_encrypt_ctr(box, input, output, err_details);
-}
-
 typedef AesNI_BoxEncryptMode AesNI_BoxDecryptMode;
 
 static AesNI_BoxDecryptMode aesni_box_decrypt_mode[] =
@@ -276,8 +241,8 @@ static AesNI_BoxDecryptMode aesni_box_decrypt_mode[] =
     &aesni_box_decrypt_ecb,
     &aesni_box_decrypt_cbc,
     &aesni_box_decrypt_cfb,
-    &aesni_box_decrypt_ofb,
-    &aesni_box_decrypt_ctr,
+    &aesni_box_encrypt_ofb,
+    &aesni_box_encrypt_ctr,
 };
 
 AesNI_StatusCode aesni_box_decrypt(