<P> Due to a block cipher 's characteristic as an invertible function , its output becomes distinguishable from a truly random output string over time due to the birthday attack . This property results in the cipher 's security degrading quadratically , and needs to be taken into account when selecting a block size . There is a trade - off though as large block sizes can result in the algorithm becoming inefficient to operate . Earlier block ciphers such as the DES have typically selected a 64 - bit block size , while newer designs such as the AES support block sizes of 128 bits or more , with some ciphers supporting a range of different block sizes . </P>
<P> Due to a block cipher 's characteristic as an invertible function , its output becomes distinguishable from a truly random output string over time due to the birthday attack . This property results in the cipher 's security degrading quadratically , and needs to be taken into account when selecting a block size . There is a trade - off though as large block sizes can result in the algorithm becoming inefficient to operate . Earlier block ciphers such as the DES have typically selected a 64 - bit block size , while newer designs such as the AES support block sizes of 128 bits or more , with some ciphers supporting a range of different block sizes . </P>
what is the primary weakness of the des block cipher
what is the primary weakness of the des block cipher
64 - bit block size , while newer designs such as the AES support block sizes of 128 bits or more
64 - bit block size , while newer designs such as the AES support block sizes of 128 bits or more