+*GET /blocklocator+size+A@token*
+
+Fetch the data block. Response returns block contents. If permission checking is enabled, requires a valid token hint.
+
+*PUT /blocklocator*
+
+Body: the block contents. Responds the block locator consisting of MD5 sum of the data, block size, and signed token hint.
+
+*POST /*
+
+Body: the block contents. Responds the block locator consisting of MD5 sum of the data, block size, and signed token hint.
+
+h2(#locator). Keep locator format
+
+BNF notation for a valid Keep locator string (with hints). For example @d41d8cd98f00b204e9800998ecf8427e+0+Z+Ada39a3ee5e6b4b0d3255bfef95601890afd80709@53bed294@
+
+<pre>
+locator ::= sized-digest hint*
+sized-digest ::= digest size-hint
+digest ::= <32 lowercase hexadecimal digits>
+size-hint ::= "+" [0-9]+
+hint ::= "+" hint-type hint-content
+hint-type ::= [A-Z]+
+hint-content ::= [A-Za-z0-9@_-]*
+sign-hint ::= "+A" <40 lowercase hexadecimal digits> "@" sign-timestamp
+sign-timestamp ::= <8 lowercase hexadecimal digits>
+</pre>
+
+h3. Token signatures
+
+A token signature (sign-hint) provides proof-of-access for a data block. It is computed by taking a SHA1 HMAC of the blob signing token (a shared secret between the API server and keep servers), block digest, current API token, expiration timestamp, and blob signature TTL.
+
+When communicating with the Keep store to fetch a block, or the API server to create or update a collection, the service computes the expected token signature for each block and compares it to the token signature that was presented by the client. Keep clients receive valid block signatures when uploading a block to a keep store (getting back a signed token as proof of knowledge) or, from the API server, getting the manifest text of a collection on which the user has read permission.
+
+Security of a token signature is derived from the following characteristics:
+
+# Valid signatures can only be generated by entities that know the shared secret (the "blob signing token")
+# A signature can only be used by an entity that also know the API token that was used to generate it.
+# It expires after a set date (the expiration time, based on the "blob signature time-to-live (TTL)")
+
+h3. Regular expression to validate locator
+
+<pre>
+/^([0-9a-f]{32})\+([0-9]+)(\+[A-Z][-A-Za-z0-9@_]*)*$/
+</pre>
+
+h3. Valid locators
+
+table(table table-bordered table-condensed).
+|@d41d8cd98f00b204e9800998ecf8427e+0@|
+|@d41d8cd98f00b204e9800998ecf8427e+0+Z@|
+|<code>d41d8cd98f00b204e9800998ecf8427e+0+Z+Ada39a3ee5e6b4b0d3255bfef95601890afd80709@53bed294</code>|
+
+h3. Invalid locators
+
+table(table table-bordered table-condensed).
+||Why|
+|@d41d8cd98f00b204e9800998ecf8427e@|No size hint|
+|@d41d8cd98f00b204e9800998ecf8427e+Z+0@|Other hint before size hint|
+|@d41d8cd98f00b204e9800998ecf8427e+0+0@|Multiple size hints|
+|@d41d8cd98f00b204e9800998ecf8427e+0+z@|Hint does not start with uppercase letter|
+|@d41d8cd98f00b204e9800998ecf8427e+0+Zfoo*bar@|Hint contains invalid character @*@|
+
+h2. Manifest v1
+
+A manifest is utf-8 encoded text, consisting of zero or more newline-terminated streams.
+
+<pre>
+manifest ::= stream*
+stream ::= stream-name (" " locator)+ (" " file-segment)+ "\n"
+stream-name ::= "." ("/" path-component)*
+path-component ::= <printable ASCII - (whitespace, "/")>+
+file-segment ::= position ":" size ":" filename
+position ::= [0-9]+
+size ::= [0-9]+
+filename ::= path-component ("/" path-component)*
+</pre>
+
+Notes:
+
+* The first token is the stream name, consisting of one or more path components, delimited by @"/"@.
+** The first path component is always @"."@.
+** No path component is empty.
+** No path component following the first one can be "." or "..".
+** The stream name never begins or ends with @"/"@.
+* The next N tokens are "keep locators":#locator
+** These describe the "data stream". By logically concatenating the blocks in the order that they appear, we can refer to "positions" in the data stream.
+* File tokens come after the sequence of keep locators.
+** A file token has three parts, delimited by @":"@: position, size, filename.
+** Position and size are given in decimal
+** The position is the position in the data stream
+** The size is the count of bytes following the position in the data stream. A file size may cross multiple blocks in the data stream.
+** Filename may contain @"/"@ characters, but must not start or end with @"/"@, and must not contain @"//"@.
+** Filename components (delimited by @"/"@) must not be @"."@ or @".."@.
+** There may be multiple file tokens.
+
+It is legal to have multiple file tokens in the manifest (possible across different streams) with the same combined path name @stream name + "/" + filename@. This must be interpreted as a concatenation of file content, in the order that the file tokens appear in the manifest.
+
+Spaces are represented by the escape sequence @\040@. Spaces in stream names and filenames must be translated when reading and writing manifests. A manifest may not contain TAB characters, nor other ASCII whitespace characters or control codes other than the spaces or newlines used as delimiters specified above. A manifest always ends with a newline -- except the empty (zero-length) string, which is a valid manifest.
+
+h3. Normalized manifest v1
+
+A normalized manifest is a manifest that meets the following additional restrictions:
+
+* Streams are in alphanumeric order.
+* Each stream name is unique within the manifest.
+* Files within a stream are listed in alphanumeric order.
+* Blocks within a stream are ordered based on order of file tokens of the stream. A given block is listed at most once in a stream.
+* Filename must not contain @"/"@ (the stream name represents the path prefix)