So,deepcoin algo is even weaker than NIST5 ,qubit,right? coz it's only 3 parts of X11,NIST5 ,qubit are both 5 parts of X11.
Ah, no, you can't make that comparison, it doesn't work that way.
That's a wee bit like saying if it takes 4 and half minutes to soft-boil an egg then soft-boiling half a dozen eggs should take just short of half an hour.
But yes, the situation is a little confused/confusing.
As far as I understand it, the absolute basics for altcoin crypto are:
256-bit crypto is appropriate for the task and good until 2040 at leastECRYPT II's 2012 annual review of key lengths opines “Good, generic application-independent recommendation, ≈ 30 years” and that’s just for
128-bit, for 256-bit they state “Good protection against quantum computers unless Shor’s algorithm applies.”
one round of hashing is adequate to secure the blockchainHashing the result of a hash brings no gain in security. It seems that the otherwise-inexplicable double round of SHA256 hashing in classic Bitcoin is a simple-but-tricksy way of defending against the threat of a possible length extension attack which was was being discussed at the time but which subsequently came to naught.
The multi-hash approach was first used in
SiFcoin (google translated): “Complication chain to the length of 6 different hash functions and increase bit depth to intermediate 512 - attempt to protect from further development of extremely efficient Mh / s gpu-algorithms and theory, "simple" Gh / s devices”.
Note, no mention at all made of security, just a possibility of limiting GPU advantage (and a dubious possibility at that). But somehow, this tactic to limit GPU advantage has mutated into security theatre cryptobabble: “super secure hashing” (Quark), “X15 adds 2 extra layers of hashing to the popular and already very secure X13 hashing Algorithm” (Maiacoin).
There's a pertinent stackexchange discussion
Guarding against cryptanalytic breakthroughs: combining multiple hash functions. The posts by Zooko and by Thomas give a realistic appreciation of the issues.
When it's boiled down to the essence: for an altcoin, a tactic of chaining hash algos can't be proven to increase security nor can the tactic be proven not to reduce security. This latter weakness is usually considered a FAIL in crypto best practice.
The sole purpose of chaining hash functions is to protect mining from being overwhelmed by specialist hardware advantage. Any mention of enhanced security is either a misconception or simply cryptobabble and, for either reason, disheartening to see in an [ANN].
Cheers
Graham