The problem with this is you have created a pattern which could (and probably does) introduce a cryptographic weakness. If someone knew or could guess you were using this tactic then they might be able to exploit it.
While I don’t have an example of a specific weakness to MD5 to hand one of the basic rules of exploiting algorithms is knowing some of the source material or knowing about patterns within it.
The point of using a salt is to use a piece of unknown material which is unique in each string. It’s common to generate random junk to use rather than anything meaningful.
Personally I always take "new insight" into security tactics with a pinch of salt until they have been hammered on by a few people.
Comments
To repeat the comment I made on the site:
The problem with this is you have created a pattern which could (and probably does) introduce a cryptographic weakness. If someone knew or could guess you were using this tactic then they might be able to exploit it.
While I don’t have an example of a specific weakness to MD5 to hand one of the basic rules of exploiting algorithms is knowing some of the source material or knowing about patterns within it.
The point of using a salt is to use a piece of unknown material which is unique in each string. It’s common to generate random junk to use rather than anything meaningful.
Personally I always take "new insight" into security tactics with a pinch of salt until they have been hammered on by a few people.