Re: Encryption size

From: Unruh (unruh-spam_at_physics.ubc.ca)
Date: 10/29/05

  • Next message: Ertugrul Soeylemez: "Re: Encryption size" 
    Date: 29 Oct 2005 16:35:53 GMT

    Lassi =?ISO-8859-15?Q?Hippel=E4inen?= <lahippel.at.ieee.org@moon.invalid> writes:

    >Ertugrul Soeylemez wrote:

    >> Lassi Hippeläinen <lahippel.at.ieee.org@moon.invalid> (Tue, 25 Oct 2005
    >> 15:16:12 +0300):
    >>> frank wrote:
    >>> > Can anyone tell me what size a 16-byte MD5 or 20-byte SHA-1 message
    >>> > digest will encrypt to using the RSA algorithm? Will they still be 16
    >>> > bytes or 20 bytes respectively? Or will they get any larger?
    >>>
    >>> They will be rounded up to the next full block. The block size is one
    >>> design parameter that you can choose within some limits.
    >>
    >> That's wrong. The new size will be the size of your RSA modulus.

    >RSA can be seen as a block cipher. The block size is the size of the
    >modulus, which you can choose.

    But if you choose it to be only 20 bytes, you may as well not use
    encryption. RSA is absurdly weak at that size.

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