Blockchain-based financial systems must balance two competing needs: the transparency that lets anyone verify the public ledger, and the privacy needed to stop transactions from being tied to real-world identities. A ring signature authenticates a transaction while concealing the true signer among a set of public keys (the ring), offering unconditional privacy without losing verifiability. Ring signatures built on RSA or standard ECDSA have sizes that grow linearly with the ring, which restricts how large the anonymity set can practically be. We propose a Concise Linkable Spontaneous Anonymous Group Signature (CLSAG) construction over elliptic curves, with O(n) signature size and a constant-factor gain in verification time obtained by algebraically optimising the key image computation. The discrete algebraic ring structure of the elliptic curve group allows several partial signatures to be compressed into one aggregated proof via a polynomial commitment scheme, which cuts signature size by 47% relative to MLSAG at equal ring size. Unforgeability, anonymity and linkability are proved formally under the discrete logarithm assumption in the random oracle model. On a Monero-compatible blockchain testnet with ring size 16, the scheme yields a 1.4 KB signature, 3.7 ms signing time, 2.4 ms verification time and 47 transactions per second, a 2.0× improvement over MLSAG across all metrics. It also supports stealth addresses and key images that block double spending while keeping the signer unconditionally anonymous.