Base64 adds padding using the '=' character. This is almost correct, except: what if the length of the data doesn't nicely line up to a multitude of 3? Then you cannot get a nice set of four 6-bit numbers. For each of those sets, you know you have 3 bytes of original data 3 * (LengthInCharacters / 4) = length in bytes To calculate the length of the original data, you must count how many sets of 4 characters are in the Base64 string. So four characters of base64 represent 3 bytes of data. A 6-bit number can represent 64 possible value.Įach possible value corresponds to an ascii character. As described above, increasing Base64 encoding longer fixed prefix stronger attack detection fingerprint. ![]() To encode, it splits up the three bytes into 4 6-bit numbers. The input is a set of bytes: īase64 uses 4 ascii characters to encode 24-bits (3 bytes) of data. Latest 25 from a total of 2,180 transactions (+ 6 Pending ) Txn Hash. To know the length of the original data, we must understand how Base64 works. Putting binary data inside an xml file, for example, could act weird, but a Base64 string acts just like normal text.Ī base64 string looks like this: TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWFzb24sIGJ1dCBieSB0aGlzIHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhlciBhbmltYWxzLCB3aGljaCBpcyBhIGx1c3Qgb2YgdGhlIG1pbmQsIHRoYXQgYnkgYSBwZXJzZXZlcmFuY2Ugb2YgZGVsaWdodCBpbiB0aGUgY29udGludWVkIGFuZCBpbmRlZmF0aWdhYmxlIGdlbmVyYXRpb24gb2Yga25vd2xlZGdlLCBleGNlZWRzIHRoZSBzaG9ydCB2ZWhlbWVuY2Ugb2YgYW55IGNhcm5hbCBwbGVhc3VyZS4= The goal is to make it easier to transfer. Return (3 * (characterCount / 4)) - paddingCount īase64 is a way to encode binary data in ascii data. Var paddingCount = base64string.Substring(characterCount - 2, 2) Var characterCount = base64string.Length Here's a function in C#: public int GetOriginalLengthInBytes(string base64string) To get the length of bytes we use the formula: (3 * (LengthInCharacters / 4)) - (numberOfPaddingCharacters) This not only increases your bandwidth bill, but also increases the download time. Sometimes, padding is added in the form of one or two '=' characters. Does Base64 encoding reduce size Although Base64 is a relatively efficient way of encoding binary data it will, on average still increase the file size for more than 25. ![]() Alphanumeric characters are typically stored in one byte (8 bits), so since 6 bits of binary map to 8 bits of Base64, the file size will increase by about a third. A question was posed today: can I get the exact length in bytes of the input data, if I have a Base64 string?īase64 encodes three bytes to four characters. Base64 converts every 6 bits of binary into an alphanumeric character (6 bits can hold 64 different values, hence the name).
0 Comments
Leave a Reply. |