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| author | Sybren A. Stüvel <sybren@stuvel.eu> | 2016-01-22 13:11:22 +0100 |
|---|---|---|
| committer | Sybren A. Stüvel <sybren@stuvel.eu> | 2016-01-22 13:14:40 +0100 |
| commit | 2310b34bdb530e0bad793d42f589c9f848ff181b (patch) | |
| tree | 7add9af08619ac491dadef6c0a9620794e5b68bd /rsa/pkcs1.py | |
| parent | 15b69b38568cfe883180c397d408207b456e0e06 (diff) | |
| download | rsa-git-2310b34bdb530e0bad793d42f589c9f848ff181b.tar.gz | |
Fix #19: Implemented blinding when decrypting.
This prevents side-channel (such as timing) attacks, see:
https://en.wikipedia.org/wiki/Blinding_%28cryptography%29
Diffstat (limited to 'rsa/pkcs1.py')
| -rw-r--r-- | rsa/pkcs1.py | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/rsa/pkcs1.py b/rsa/pkcs1.py index 7d6814c..0b7982c 100644 --- a/rsa/pkcs1.py +++ b/rsa/pkcs1.py @@ -229,8 +229,14 @@ def decrypt(crypto, priv_key): blocksize = common.byte_size(priv_key.n) encrypted = transform.bytes2int(crypto) - decrypted = core.decrypt_int(encrypted, priv_key.d, priv_key.n) - cleartext = transform.int2bytes(decrypted, blocksize) + + # Perform blinded decryption to prevent side-channel attacks. + # See https://en.wikipedia.org/wiki/Blinding_%28cryptography%29 + blinded = priv_key.blind(encrypted, 4134431) # blind before decrypting + decrypted = core.decrypt_int(blinded, priv_key.d, priv_key.n) + unblinded = priv_key.unblind(decrypted, 4134431) + + cleartext = transform.int2bytes(unblinded, blocksize) # If we can't find the cleartext marker, decryption failed. if cleartext[0:2] != b('\x00\x02'): |