Blockchain technology, known for its decentralized and tamper-resistant nature, offers strong auditing guarantees across a wide range of applications. However, its inherent immutability presents challenges when correcting erroneous transactions or removing sensitive information is necessary. To address this, the concept of redactable blockchain has emerged, aiming to improve adaptability to real-world regulatory and operational needs. Yet, existing designs often suffer from limitations in decentralization, security, or efficiency. This paper introduces an Enhanced Threshold Chameleon Hash (ETCH) scheme as a foundational building block for redactable blockchains. ETCH enables redactions only when a predefined threshold of nodes collaborates to generate trapdoor shares, preserving decentralization. It also enhances collision resistance, overcoming key security flaws in prior schemes, and incorporates a periodic trapdoor refresh mechanism to improve long-term robustness. Experimental results show that ETCH reduces computational overhead by 50% in Hash and Verify phases and by 22.26% in the Adapt phase. The prototype implementation of the ETCH-based redactable blockchain further confirms ETCH's effectiveness in supporting low-latency redactions and mitigating blockchain state growth. Overall, ETCH improves both the security and efficiency of redactable blockchains, broadening their applicability in privacy-sensitive and regulated scenarios.