[OT] Interference by multiple encryption.

[Jan Luehr <jluehr@xxxxxxx>]

Hello,

I recently wondered if multiple encryption can decrease the security of 
encrypted information.
Imho we can basically think of two different scenarios:
1st. Encrypting information twice.
For instance: An RSA encrypted mail is stored on a loop-aes encrypted 
harddrive. (If you think of XOR, you run into serious problems, if using same 
keys, but I guess RSA and AES won't be a problem at all.)

2nd. Encrypting information more times.
For instance: Backups are done on removeable media. Each one is encrypted with 
a different set of keys for loop-aes, but also containing very similar data.

Do you know, serious studies or trust-/helpful reports,  etc. on what 
algorithmens / implementations can / should / mustn't be combined and how 
multiple encryption effects security?

Thanks in advance.
Keep smiling
yanosz

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Linux-crypto:  cryptography in and on the Linux system
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