Small unique hash for Strings???

I have a list of Strings that can have maximum length 25.
I want to map each String to another unique String that is 25 character long.
One way i try was to use md5 (Java Security API) but the md5 hash(in hex) generated for
each String was around 40 character long! but i only have 25 character length
(yes i can not increase it due to some reason).
Is there any way to map a String on another hash or String that is unique?
regards,
TH

well, the md5 hash is 16 bytes. You can encode this as 32 characters using ASCII hex encoding. You can then keep the first 25 bytes and throw the rest away. That is one solution.
A better solution is to base64 encode the md5 hash. The base64 encoding of 16 bytes takes only 22 characters, so this is better.
When using md5, or any other cryptographic hash function, there is very small probability of having two strings hash to the same value at random. Using the methods outlined above, this probability is neglible. However, there are recent cryptanalytic results on md5 and even sha1 that show that, in certain scenarios, it may be much easier to choose a string that hashes to the same value as another string.
Perhaps the best option is to investigate algorithms for constructing what are called perfect hash functions. Just google "perfect hash function".

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Unique Hash Codes

Hi
I'm interested to know what the maximum String length is to guarantee a
unique hashCode for each possible String value?
Also, how would one go about calculating this value?
Thanks

JoachimSauer wrote:
As you noted yourself a perfect hash is usually not necessary.
But the answer is easy: a char are 16 bit in Java. A hashCode is an int, which is 32 bit. So you can only guarantee a perfect hash for Strings of length <= 2. Note that the hashCode() implementation in String does not implement such an algorithm, so you can even have collisions with 2 characters.So the answer is 1 ;-)

"buffer too small for string or missing null byte" inserting CR in excel

I have created a Crystal Report based on below stored procedure.
DELIMITER $$
DROP PROCEDURE IF EXISTS `ww_test`.`PRD_Data_sp` $$
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BEGIN
select
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               WHEN groupby='SalesOrg' THEN CONCAT(p.VKORG,'_',p.VTWEG)
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An error occurred while opening the report. The report does not exist; you have insufficient rights to open the report; or you cannot make a connection to the BusinessObjects Web Service. (LO 02010)
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Crystal Reports 2008
Live Office XI 3.1
BOEdge XI 3.1
Xcelsius 2008
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With the CurrentValue method
Crpt.ParamFields[3].CurrentValue := memo1.Text;
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Buffer too small for string - Crystal Report for Vs2010

Hello,
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Thank you.
Charles

Hello Don,
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   CrystalDecisions.Shared, Version=13.0.2000.0
I have then try the following code and found out the limit of ReportComment is 511 but in the Crystal Report 2008 designer and runtime the limit did not apply.
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Thank you.
Charles
<code> should be
Edited by: Don Williams on Feb 4, 2011 12:47 PM

Generate Unique Hash Key in PL/SQL

I have a document that i want to send to certain customers. What I've decided to do is send the customer a link to the document that will be stored locally on our server. Obviously for security reasons i don't want to simply send the sequential doc ID allowing customers to change the query string to get other information.
What would be the best way in pl/sql to generate a unique hash key to include in the url? The key would have to be both unique and not easily edited by customers to view other documents.
Any help would be much appreciated.
Faoilean.

faoilean wrote:
I've been experimenting with SHA-1 and it works very well in producing a 40 character hash. My one concern is that for example hashing '1025' produces the following hash 'B74E9CAD775D997FC742B45E1BA7BD5295D63D13'.
Would someone not just simply be able to use SHA-1 to create a hash for '1026' (since i'm using a sequential number for my input) and consequently retrieve somebody elses information and leave my system vulnerable?
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If you really want to be sure then you could also also incorporate the date/time of the document into the string that you hash, so they would have to a) have access to the dbms_crpto package, b) know the filename and the date/time of the document and c) know what order to combine those things (and the format mask you've used on the date/time etc.) to provide the correct hash to obtain the document.
If you use encryption then you leave yourself open to decryption.
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I think you'll find when it comes to things like password storage, most will use a 1 way hash (or similar) algorithm rather than an encrypted password so that the stored passwords can never be reverse engineered. Also, such password algorithms usually combine the username or some other feature to prevent two users with the same password getting the same hash value.

How to Genarate a Unique ID for each Payload in XI

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Hi Amaresh !
XI generates and stamps a messageID to each message header. That ID is unique. You could use that one. To get that number from inside message mapping to put it in the payload, you could use a java UDF with this code:
String msgid;
java.util.Map map;
map = container.getTransformationParameters();
msgid = (String) map.get(StreamTransformationConstants.MESSAGE_ID);
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Hashing a string

Using Oracle 10g R2.
I want to hash a string using SHA-1 and the documentation that comes with 10g R2 talks about using the DBMS_CRYPTO package. It apparently has a nice little Hash function where you pass it your string and the type of crypto you want to use.
Unfortunately there isn't a DBMS_CRYPTO package.
There is however a DBMS_CRYPTO_TOOLKIT package which also has a Hash function in it, but this seems to take a few more parameters including "Persona"'s etc. and there's no documentation on this package included in the Oracle documentation.
All I want to do is generate a SHA-1 hash value for a string.
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Cheers

Through both TOAD and SQL*Plus (logged on as sys user) it doesn't exist...
(output from SQL Plus session)
SQL> exec dbms_crypto.hash('a');
BEGIN dbms_crypto.hash('a'); END;
ERROR at line 1:
ORA-06550: line 1, column 7:
PLS-00201: identifier 'DBMS_CRYPTO' must be declared
ORA-06550: line 1, column 7:
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BEGIN dbms_crypto_toolkit.hash('a'); END;
ERROR at line 1:
ORA-06550: line 1, column 7:
PLS-00306: wrong number or types of arguments in call to 'HASH'
ORA-06550: line 1, column 7:
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Generate unique 10 char string

Hi,
i have to generate a unique 10 char string ( a string with length of 10 ) which has numbers and alphabets with no special characters, is there any code of doing it
Ashish

class UniqueString {
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private static int[] lastString = new int[NUM_CHARS];
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"0123456789abcdefghijklmonpqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
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ca[index]=0;
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Guarenteed to be unique within one VM instance.
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Hi,
in some generic classes we display internal tables in a grid. We want to activate the save&maintain layouts feature by passing the DISVARIANT structure, Here wen have to give Report and handle. As we display some more tables using the same method, we must set a unique handle so that saved ALV layouts do not get merged /confused. As we do not have a table name at this point, my idea is to create a hash key based on the fields in the field catalog (field catalog is only distinguishable object here).
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Please: Serious answers only.
Regards,
Clemens

Here it is
function enqueuecomputehash.
*"*"Lokale Schnittstelle:
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*"     VALUE(INPUT) TYPE STRING
*"     VALUE(INPUT_LEN) TYPE I
*"     VALUE(HASH_LEN) TYPE I
*" EXPORTING
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*"     REFERENCE(TIME_USEC) TYPE I
*" EXCEPTIONS
*"      INVALID_ARGUMENT
field-symbols <text>.
field-symbols <hash>.
data: tmp_input type text8192.
data: tmp_hash type text8192.
if input_len < 1 or hash_len < 1.
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endif.
assign tmp_input(input_len) to <text>.
assign tmp_hash(hash_len) to <hash>.
data: t1 type i,
      t2 type i.
<text> = input.
get run time field t1.
call 'C_ENQ_WILDCARD' id 'TEXT'     field <text>
                      id 'TEXTHASH' field <hash>.
get run time field t2.
hash = <hash>.
time_usec = t2 - t1.
endfunction.

Compareto versus equals performance for strings equality

Hi
Just wanted to know whether compareto and equals method performance for checking whether the two strings are equal or not .
Which one is good with respect to bytecode , speed performance.
Im not asking for the difference, only asking which one is good to use most number of times for comparing two strings for equilaty.
Thanks.

Hi
Ya they are both for different purposes. No doubt.
t which one is faster among the two for string
equality?
compareto or equals.
thanksHis point is that it doesn't matter. You shouldn't worry about optimization for small details like this. Unless you are profiling your code and find a large slowdown with that code, then don't worry about their performance. Use the one that best suits your purpose. If you want to know if they're equal, use equals(), if you want to know their order, use compareTo().

Does anybody know a reliable hashCode-function for strings?

Hello,
I would like to exchange hashcodes between clients and server, both running at different jre's (even msjvms are running it) - and for the same string they should be identical.
Javadoc mentions that Object.hashCode() may vary from imlpementation, but I would need an implementation which would be consistent across jvms.
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Thanks in advance, lg Clemens

Even the hashcode() API points out that
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address of an object, an implementation that might
differ from other JVMs. So if you'd rely on that
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* (The hash value of the empty string is zero.)
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Kaj

IPhone 6Plus on every reboot after putting in my password it opens to a small window asking for apple id password

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Unique id for calling thread

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DUAL
;

Please don't abuse the forums by posting in many places.
General Database Discussions

Unique id For System Message

Dear all,
Any one can please tell me the unique id for System Message. Also i want to know the unique id for 'yes' and 'No' in System Message. Its very urgent
Thanks in advance
with Regards
G.shankar

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Small unique hash for Strings???

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