AES encryption decryption online tool which performs encryption or decryption of an input data based on the given modes (ECB, CBC, CFB or OFB) and key bit sizes (128, 192 or 256 bits) using AES algorithm.
The encryption/decryption with a cipher key of 128, 192, or 256 bits is denoted as AES128, AES192, AES256 respectively.
AES Summary:
Name  Description 

Block size  128 bits 
key sizes  128, 192, 256 bits 
Rounds  10, 12 or 14 (depending on key size) 
Design principle  Substitutionâ€“permutation network 
Modes 

Designers  Vincent Rijmen, Joan Daemen 
Also, known for 

The Advanced Encryption Standard (AES) is a block cipher that encrypts a 128bit block (plaintext) to a 128bit block (ciphertext), or decrypts a 128bit block (ciphertext) to a 128bit block (plaintext).
AES encryption/decryption flows consists a backtoback sequence of AES transformations, operating on a 128bit State (data) and a round key. The flows depend on the cipher key length, where total transformation steps for encryption/decryption as follows 
Refer following encryption pseudo code 
Note round_key_encrypt[]
round_key_encrypt[0]
stores the first 128 bits of the 'cipher key', which is used for the first XOR operation (aka round 0).
# data is a 128bit block to be encrypted.
# The round keys are already stored in the round_key_encrypt[]
tmp = addRoundKey(data, round_key_encrypt[0])
for round = 19 or 111 or 113:
tmp = subBytes(tmp)
tmp = shiftRows(tmp)
tmp = mixColumns(tmp)
tmp = addRoundKey(tmp, round_key_encrypt[round])
end loop
tmp = subBytes(tmp)
tmp = shiftRows(tmp)
tmp = addRoundKey(tmp, round_key_encrypt[10 or 12 or 14])
result = tmp
Similarly for decryption  follow 'Inverse Cipher', where steps reversed along with invert operations e.g. invSubButes(tmp), invShiftRows(tmp), invMixColumns(tmp)
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