Further detection can be done when the block is received is different from the bit pattern received codeword sent suppose 00100th block codeword that is not a valid password. If we consider acceptable invalid password is required only changing one bit will generate the bit pattern of a valid password

Sandi block is formed principally of runs of data with fixed length (k) then add a number (nk) bits that are formed along the n codeword unique.
Hamming distance: the number of bits that are not equal between the two codeword.

C1 = 011,011, C2 = 110,001

The second codeword Hamming distance can be expressed diatasa d (C1, C2) = 3

How the addition of these bits can provide correction capability in digital data transmission can be explained in the following examples:

for example: k = 2 and n = 5 then:

blocks of data: 00 01 10 11 converted into 5 bits of data

codeword: 00000 00111 11001 11110

Further detection can be done when the block is received is different from the bit pattern received codeword sent suppose 00100th block codeword that is not a valid password. If we consider acceptable invalid password is required only changing one bit will generate the bit pattern of a valid password, which is to be 00,000 while the other valid password is required for the conversion of 00,111 bits 2, 4 bits to 11,001, and 3 bits to 11,110. We can take the conclusion that the password is accepted because it has 00,000 compared to the largest possible passwords or other illegal has the smallest Hamming distance. This is the error correction capabilities with the addition of redundant bits.

In a password with a password C1, C2, C3, ... Cs with S = 2 ^ k, the smallest distance Dmin the password stated as:

Dmin = min [d (Si, Sj)] i ≠ j

if a password meets Dmin 2t ≥ t +1 with a positive integer then the password can correct the error of ≤ t. Furthermore the relationship between Dmin and t can be expressed as follows:

t = floor (Dmin-1) / 2; to correct the error of t

t = Dmin -1; to detect the error of t

If the error occurs several Dmin then this error can only change one valid codeword into another valid codeword, while when an error occurs then the series of Dmin error will not change a valid codeword into another valid codeword.

Some considerations in designing a block code include: 

1.  for n and k, it is expected to be the largest Dmin 
2.  should be easy in penyandianya, does not require memory and processing time is much  
3.  a little bit redundant, saving bandwidth  
4.  redundant bit much, reduce the error rate