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Tweeted twitter.com/#!/StackCrypto/status/469150310024224769
Minor typo fixes, added “encryption” tag.
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e-sushi
e-sushi
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Is AES 256-256 over AES 128-128 weakening the original encryption?

When transfering data using TLS the browser and server agree the cipher suite to be used - so for example this could be chosen as AES 128-128 and is (probably) outside of my control. If I separately encrypt a file using AES 256-256 and then Alice downloads this via her browser (using AES 128) have I still effectively got AES 256-256 security?

My reasoning goes like this: even if the AES 128-128 encryption on the TLS link was broken by Eve then all she would get is the AES 256-256 encrypted file and she would then have to break that encryption to see the plaintext.

Of course the AES256AES-256 key is sent to Alice over a separate channel.

Bob

Is AES 256 over AES 128 weakening the original encryption

When transfering data using TLS the browser and server agree the cipher suite to be used - so for example this could be chosen as AES 128 and is (probably) outside of my control. If I separately encrypt a file using AES 256 and then Alice downloads this via her browser (using AES 128) have I still effectively got AES 256 security?

My reasoning goes like this: even if the AES 128 encryption on the TLS link was broken by Eve then all she would get is the AES 256 encrypted file and she would then have to break that encryption to see the plaintext.

Of course the AES256 key is sent to Alice over a separate channel.

Bob

Is AES-256 over AES-128 weakening the original encryption?

When transfering data using TLS the browser and server agree the cipher suite to be used - so for example this could be chosen as AES-128 and is (probably) outside of my control. If I separately encrypt a file using AES-256 and then Alice downloads this via her browser (using AES 128) have I still effectively got AES-256 security?

My reasoning goes like this: even if the AES-128 encryption on the TLS link was broken by Eve then all she would get is the AES-256 encrypted file and she would then have to break that encryption to see the plaintext.

Of course the AES-256 key is sent to Alice over a separate channel.

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Bob
Bob
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Is AES 256 over AES 128 weakening the original encryption

When transfering data using TLS the browser and server agree the cipher suite to be used - so for example this could be chosen as AES 128 and is (probably) outside of my control. If I separately encrypt a file using AES 256 and then Alice downloads this via her browser (using AES 128) have I still effectively got AES 256 security?

My reasoning goes like this: even if the AES 128 encryption on the TLS link was broken by Eve then all she would get is the AES 256 encrypted file and she would then have to break that encryption to see the plaintext.

Of course the AES256 key is sent to Alice over a separate channel.

Bob