Bitcoin base64 en code c

Base64 (MIME) Encode and Decode Tool

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Base64 is a group of similar binary-to-text encoding schemes that represent binary data in an ASCII string format by translating it into a radix representation. Each base64 digit represents exactly 6 bits of data. Three 8-bit bytes i. The particular set of 64 characters chosen to represent the 64 place-values for the base varies between implementations.

The general strategy is to choose 64 characters that are both members of a subset bitcoin base64 en code c to most encodings, and also printable. This combination leaves the data unlikely to be modified in transit through information systems, such as email, that were traditionally not 8-bit clean.

Other variations share this property but differ in the symbols chosen for the last two values; an example is UTF For instance, uuencode uses uppercase letters, digits, and many punctuation characters, but no lowercase. The example below uses ASCII text for simplicity, but this is not a typical use case, as it can already be safely transferred across all systems that can handle Base The more typical use is to encode binary data such as an image ; the resulting Base64 data will only contain 64 different ASCII characters, all of which can reliably be transferred across systems that may corrupt the raw source bytes.

A quote from Thomas Hobbes ' Leviathan:. In the above quote, the encoded value of Man is TWFu. Encoded in ASCII, the characters Maand n are stored as the bytes 7797andwhich are the 8-bit binary values, and These three values are joined together into a bit string, producing As this example illustrates, Base64 encoding converts three octets into four encoded characters.

If there is only one significant bitcoin base64 en code c byte e. If there are two significant input bytes e. As illustrated in the bitcoin base64 en code c table above, when the last input group contains only one octet, the four least significant bits of the last content-bearing 6-bit block will turn out to be zero:.

And bitcoin base64 en code c the last input group contains two octets, the two least significant bits of the last content-bearing 6-bit block will turn out to be zero:.

The example below illustrates how truncating the input of the above quote changes the output padding:. The same characters will be encoded differently depending on their position within the three-octet group which is encoded to produce the four characters. The ratio of output bytes to input bytes is 4: In theory, the padding character is not needed for decoding, since the number of missing bytes can be calculated from the number of Base64 digits.

In some implementations, the padding character is mandatory, while for others it is not used. One case in which padding characters are required is concatenating multiple Base64 encoded files. When decoding Base64 text, four characters are typically converted back to three bytes. The only exceptions are when padding characters exist. Without padding, after normal decoding of four characters to three bytes over and over again, fewer than four encoded characters may remain.

In this situation only two or three characters shall remain. A single remaining encoded character is not possible because a single base 64 character only contains 6 bits, and 8 bits are required to create a byte, so a minimum of 2 base 64 characters are required: Implementations may have some constraints on the alphabet used for representing some bit patterns.

This notably concerns the last two characters used in the index table for index 62 and 63, and the bitcoin base64 en code c used for padding which may be mandatory in some protocols, or removed in others. The table below summarizes these known variants, and link to the subsections below. PEM defines a "printable encoding" scheme that uses Base64 encoding to transform an arbitrary sequence of octets to a format that can be expressed in short lines of 6-bit characters, as required by transfer protocols such as SMTP.

To convert data to PEM printable encoding, the first byte is placed in the most significant eight bits of a bit bufferthe next in the middle eight, and the third in the least significant eight bits. If there are fewer than three bytes left to encode or in totalthe remaining buffer bits will be zero. The buffer is then used, six bits at a time, most significant first, as indices into the string: The process is repeated on the remaining data until fewer than four octets remain.

If three octets remain, they are processed normally. If fewer than three octets 24 bits are remaining to encode, the input data is right-padded with zero bits to form an integral multiple of six bits.

This signals the decoder that the zero bits added due to padding should be excluded from the reconstructed data. This also guarantees that the bitcoin base64 en code c output length is a multiple of 4 bytes. PEM requires that all encoded lines consist of exactly 64 printable characters, with the exception of the last line, which may contain fewer printable characters.

Lines are delimited by whitespace characters according to local platform-specific conventions. MIME does not specify a fixed length for Baseencoded lines, but it does specify a maximum line length of 76 characters.

Very roughly, the final size of Baseencoded bitcoin base64 en code c data is equal to 1. The size of the decoded data can be approximated with this formula:.

Modified Base64 simply omits the padding and ends immediately after the last Base64 digit containing useful bits leaving up to three unused bits in the last Base64 digit. Unless implementations are written to a specification that refers to RFC and specifically requires otherwise, RFC forbids implementations from generating messages containing characters outside the encoding bitcoin base64 en code c or without padding, and it also declares that decoder implementations must reject data that contain characters outside the encoding alphabet.

Base64 encoding can be bitcoin base64 en code c when fairly lengthy identifying information is used in an HTTP environment. Also, many applications need to encode binary data in a way that is convenient for inclusion in URLs, including in hidden web form fields, and Base64 is a convenient encoding to render them in a compact way.

XML identifiers and name tokens are encoded using two variants:. The atob and btoa JavaScript methods, defined in the HTML5 draft specification, [10] provide Base64 encoding and decoding functionality to web pages. The btoa method outputs padding characters, but these are optional in the input of the atob method.

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Retrieved March 18, Message Encryption and Authentication Procedures. Format of Internet Message Bodies. World Wide Web Consortium. Retrieved 2 January Introduced by changeset Bitcoin base64 en code c from " https: Views Read Edit View history.

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Join Stack Overflow to learn, share knowledge, and build your career. I have binary data in an unsigned char variable. I need to convert them to PEM base64 in c. I looked in openssl library but i could not find any function. Does any body have any idea? Keep in mind that this doesn't do any error-checking while decoding - non base 64 encoded data will get processed. But you can also do it in openssl openssl enc command does it I know this question is quite old, but I was getting confused by the amount of solutions provided - each one of them claiming to be faster and better.

I put together a project on github to compare the base64 encoders and decoders: Also tests were conducted using Visual Studio The two fastest encoder implementations I found were Jouni Malinen's at http: Here is the time in microseconds to encode 32K of data using the different algorithms I have tested up to now:.

Here are the decoding results and I must admit that I am a bit surprised:. None of answers satisfied my needs, I needed simple two-function solution for encoding and decoding, but I was too lazy to write my own code, so I found this:. It is lightweight and perhaps the fastest publicly available implementation. It's also a dedicated stand-alone base64 encoding library, which can be nice if you don't need all the other stuff that comes from using a larger library such as OpenSSL or glib.

You can also play around on your own, e. Know ye all persons by these presents that you should not confuse "playing around on your own" with "implementing a standard.

The performance boost is acieved by using a lookup table for encoding and decoding. You'll need to link with the "crypto" library which is OpenSSL. This has been checked for leaks with valgrind although you could add some additional error checking code to make it a bit better - I know at least the write function should check for return value. Small improvement to the code from ryyst who got the most votes is to not use dynamically allocated decoding table but rather static const precomputed table.

Another solution could be to use std:: Here is an optimized version of encoder for the accepted answer, that also supports line-breaking for MIME and other protocols simlar optimization can be applied to the decoder:. Thank you for your interest in this question. Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site the association bonus does not count.

Would you like to answer one of these unanswered questions instead? Email Sign Up or sign in with Google. How do I base64 encode decode in C? I have a github repository with tested base64 and unbase64 functions. The only header you need is base Here's the one I'm using: It doesn't make any sense to use this if there is a library. You can skip the libm and math. I realize it is "no error checking", but especially notice that although the decoding table in the decoder is an array of , since char is signed on most architectures, you are really indexing from to Any character with the high bit set will cause you to read outside the allocated memory.

Forcing the data lookup to be an unsigned char clears that up. You still get garbage out for garbage in, but you won't segfault. Together with all other errors a pretty bad implementation. Piotr Lesnicki 6, 2 23 Here is the time in microseconds to encode 32K of data using the different algorithms I have tested up to now: Here is the one from Jouni Malinen that I slightly modified to return a std:: Slightly modified to return a std:: Here are the decoding results and I must admit that I am a bit surprised: Here is the code for the sake of completeness: GaspardP 1, 10 I really don't think std:: Aug 23 '17 at While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference.

Link-only answers can become invalid if the linked page changes. None of answers satisfied my needs, I needed simple two-function solution for encoding and decoding, but I was too lazy to write my own code, so I found this: Putting the code below in case the site goes down: In no event will the author be held liable for any damages arising from the use of this software.

Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions: The origin of this source code must not be misrepresented; you must not claim that you wrote the original source code. If you use this source code in a product, an acknowledgment in the product documentation would be appreciated but is not required.

Altered source versions must be plainly marked as such, and must not be misrepresented as being the original source code. This notice may not be removed or altered from any source distribution.

Dan Moulding k 15 82 After an hour of debugging I figured out that libb64 assumes that char is signed on the target system Note the sourceforge implementation adds newlines which are not universally supported. A fork by BuLogics on github removes them, and I've generated a pull request based on your extremely useful finding, Noir.

Norman Ramsey k 50 Here is a list of base64 encoding variants. I do not see a base64 encoding variant with the ordering of characters you use.

But the math behind the algorithm is correct. Here's my solution using OpenSSL. Necessary for b64 encoding, because of pad characters. On the "Adds a null-terminator" line I get an AddressSanitizer error that the write overflows the heap by 1 byte. Thanks, I have corrected the error, in addition to doing extensive testing with randomly-sized strings of random bytes to ensure that the code works as advertised. I compiled it with cc -o base base. It produced this output: Original character string is: Base64 encode this string!

Base encoded string is: Here's the decoder I've been using for years LarryF 3, 3 22 It's just a very simple operation that makes sure the dest buffer is set to NULL in case the caller did not do that before the call, and if perhaps the decode failed, the returned buffer would be zero length. I didn't say I debugged, traced, and profiled this routine, it's just one I've been using for years. Maybe I'll just edit it out. Thanks for pointing it out! Yeah, caused nasty bug in our app. Hi Larry, thanks for sharing you code.

Added code inline by request. The linked blog no longer seems to exist at that URL. HulkHolden It's still available here tmplusplus. Homer6 9, 8 45 Your current implementation has a memory leak. The decoding table is computed as follows: Here is an optimized version of encoder for the accepted answer, that also supports line-breaking for MIME and other protocols simlar optimization can be applied to the decoder: Amit Bens 1 8 Stack Overflow for Teams is Now Available.

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