Tool to decrypt/encrypt with base 64. Base64 is a coding system using 64 characters, selected to be compatible with a majority of coding tables. It is used with emails for example.

Base64 Coding - dCode

Tag(s) : Character Encoding, Internet

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Tool to decrypt/encrypt with base 64. Base64 is a coding system using 64 characters, selected to be compatible with a majority of coding tables. It is used with emails for example.

**Base 64** encoding requires a binary input. For a text, the values depend on its coding (often ASCII or Unicode).

__Example:__ To code DCODE that is written 01100100 01000011 01101111 01100100 01100101 in binary (ASCII code)

**Base 64** Coding starts by splitting the binary code in groups of 6 bits, filling it with 0 if needed.

__Example:__ Split as 011001 000100 001101 101111 011001 000110 0101 (+00)

Each group of 6 bits has a base 10 value, it corresponds to a character in the **Base 64** alphabet (start at 0): ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

0 | A | 1 | B | 2 | C | 3 | D | 4 | E | 5 | F | 6 | G | 7 | H |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

8 | I | 9 | J | 10 | K | 11 | L | 12 | M | 13 | N | 14 | O | 15 | P |

16 | Q | 17 | R | 18 | S | 19 | T | 20 | U | 21 | V | 22 | W | 23 | X |

24 | Y | 25 | Z | 26 | a | 27 | b | 28 | c | 29 | d | 30 | e | 31 | f |

32 | g | 33 | h | 34 | i | 35 | j | 36 | k | 37 | l | 38 | m | 39 | n |

40 | o | 41 | p | 42 | q | 43 | r | 44 | s | 45 | t | 46 | u | 47 | v |

48 | w | 49 | x | 50 | y | 51 | z | 52 | 0 | 53 | 1 | 54 | 2 | 55 | 3 |

56 | 4 | 57 | 5 | 58 | 6 | 59 | 7 | 60 | 8 | 61 | 9 | 62 | + | 63 | / |

__Example:__ The conversion from 011001 to base 10 is 25 and in the alphabet 25 is Z, 000100 is 4, etc. to obtain the characters numbered 25 4 13 47 25 6 20 or the coded message: ZENvZGU

**Base 64** only works with groups of 4 characters, if needed, fill with =.

__Example:__ Finally ZENvZGU (that had 7 chars) becomes ZENvZGU= (8 chars, a multiple of 4) which is the final **base64** encoded message.

Decryption consists in finding back values of the letters in the **Base64** alphabet: ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ (equal sign = is ignored)

__Example:__ A coded message is YjY0, corresponding values of Y,j,Y,0 in the alphabet are: 24,35,24,52

Values are converted to 6-bit binary.

__Example:__ 24 is converted 011000, 35 = 100011, etc. the decoded binary message is 011000100011011000110100

**Base64** decoding is then complete. Binary message is then read using the desired coding system (ASCII, Unicode, etc.)

__Example:__ In ASCII, 01100010,00110110,00110100 corresponds to the plain text b,6,4

The message is theoretically composed of a number of characters multiple of 4. To this end, the presence of characters = (equal) at the end of the message is a big clue.

The message has a maximum of 65 distinct characters (and possibly space or line break). By default it is: ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=

**Base64** is typically used in emails for non-ASCII messages and attachments (via the MIME standard: Multipurpose Internet Mail Extensions)

The Usenet network used **Base64** to transfer files, any indication referring to it is a clue.

Several signatures of users or sites are associated with **Base64** as code 6.0 (94/25) or the .b64 extensions

In **Base64**, 4 ASCII characters are used to code 3 bytes. Volume is increased by 33%.

__Example:__ **Base64** (6 characters) is coded QmFzZTY0 (8 characters or +33%)

**base64** (no uppercase) is coded YmFzZTY0

The **base64** uses a sixty-four character alphabet to code any binary string (in base 2), so it is a mathematical conversion to **base 64**.

Characters 62 + and 63 / can cause problems with URL, they can be remplaced by respectively - and _. The equal = sign is deleted.

RFC 2045 norm officialising **Base64** is from 1996

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