Kumar, who served in the Central Bureau of Investigation and retired as the Delhi police commissioner two years ago, said the funds were raised from a kidnapping and handed over to the chief of the 9/11 attackers Mohammad Atta by terrorist Omar Sheikh who was released by India in exchange of hijacked Indian Airlines plane in 1999.
Sheikh was given the money by terrorist Aftab Ansari, who was responsible for the attack on the American Center in Kolkata, says the 1976-batch Indian Police Service officer citing information obtained from Harkat-ul Mujahideen terrorist Asif Raza Khan.
Asif Raza said his "boss Aftab Ansari had shared the ransom money collected in the kidnapping of Partha Pratim Roy Burman, chairman–cum–managing director of Khadim Shoes with Omar Sheikh," according to Kumar. Ansari is awaiting hanging in a West Bengal jail for the AmericanCenter attack.
"Part of the ransom money received in the Burman kidnapping -- about $100,000 (at the time Rs 49 lakh) -- had later found its way from Omar Sheikh to Mohammad Atta, the chief of the 9/11 attackers," the book says.
Kumar, who is at present heading the anti-corruption wing of the Board Of Control For Cricket In India, said the revelation of Asif Raza Khan that ransom money was passed on to Mohammed Atta was mentioned in the testimony of John S Pistole, deputy assistant director, Counter terrorism Division of the Federal Bureau of Investigation before the Senate Committee on Terrorist Financing in July 2003 at Washington.
In his tell-all book on underworld activities post-1993 Bombay blasts, Kumar narrates many spine-chilling incidents of chase, plans, bureaucratic wrangling and finally his telephonic conversations with India's most wanted terrorist Dawood Ibrahim.
"It's only an attempt to share my story, my experiences and some of my cases which have no bearing on national security," he says.
In the book, he also mentions a call he had received towards the fag end of his career when he led an operation in which some of the cricketers were arrested for alleged spot-fixing during the T-20 tournament.
"I think it was Dawood or his brother Anees who told me that I should stop chasing them as I was about to retire," remembers Kumar with a smile on his face.
Coming to the narration of his conversations with Dawood Ibrahim, Kumar said the notorious underworld don was connected to him by one of the suspects in the 1993 Bombay blasts.
He recalled that his first conversation with Dawood started on a rather awkward note.
"Haan batayiye, aap mujhe kuchh batana chahte hain, jaisa Manish (the intermediatory) ne mujhe kaha hai. (I understand from Manish that you have something to tell me. So, go ahead)," the police officer told Dawood.
Dawood spoke in a typical Mumbai accent, with confidence and an "utter lack of fear and made no attempt to please me," and simply said "Saheb, iske pehle ki main kuchh bataoon, pehle aap batayiye ki aapko kya lagta hai ki maine Mumbai mein blast karwaye hain?’ (Sir, before I tell you anything, would you please tell me whether you too feel that I organised the blasts in Mumbai?).
"I had to counter him by telling him that you cannot reply to a question by posing a question," he recalled.
Kumar, who was posted as deputy inspector general in the newly-constituted Special Task Force in the CBI looking after the Bombay blasts, said he had kept his senior in loop about his conversation with Dawood.
During his three conversations with Dawood, he said the underworld don was making alibis to distance himself from the 1993 serial blasts.
"When I asked Dawood if he could deny Anees (his borther) sending weapons to (filmstar) Sanjay Dutt, he confirmed that the film star had indeed been sent arms by his younger brother.
"However, that had nothing to do with the blasts. Sanjay had come in close contact with Anees Ibrahim during the shooting of the film Yalgaar in Dubai. The actor had requested Anees to send weapons to him for his own security and for the security of his family members in the wake of the communal riots in Mumbai," he said.
Dawood claimed in the conversation that he had beaten up Anees for sending weapons to Dutt without his knowledge but the game of the underworld don "was to convince me that he was being honest. He knew that in the process he had gone to the extent of implicating his own brother."
However, it all ended with Kumar receiving orders from one of the superiors to stop communicating.
"The reasons best known to him (senior)," the police official said, adding perhaps "my senior was wary of Indian intelligence agencies overhearing the ongoing dialogue and taking objection to my transgressing their turf. The unwritten code between federal agencies in India is that the CBI sticks to investigation while the intelligence agencies carry out covert operations.
"My superior had worked in one such organisation for several years and perhaps felt such 'adventurism' was best left to the other agencies. Be that as it may, that was the end of my tete-a-tete with Dawood."
The former police commissioner refused to name the superior saying this is "unethical. As police officers we are supposed to take orders from seniors and obey them. I followed the same principle."
After many years, Dawood's name again surfaced in IPL T-20 tournament, Kumar wrote in his book and added "one day I received a call on my personal mobile in the last week of June 2013 from an 'unknown number'. It was in all probability the Don himself.
"He said 'Kya, saheb, aap retire hone ja rahe ho. Ab to peechha chhod do.’ (What is this, sir? You are about to retire. Isn't it time you left me alone?)
"The caller hung up before I could respond. I smiled to myself bemusedly at the veiled threat reminding me of my impending retirement and the subsequent stripping of my security cover," he said.
In his book, the former Delhi police chief spoke about Yakub Memon, who was hanged earlier this year for his role in the Bombay blasts that killed 257 people.
He wrote about the brain game played with Pakistan's Inter-Services Intelligence in bringing Memon family to India from Dubai and also attempted to put a lid on the controversy that Memons were brought on a deal that a lenient view will be taken.
"Truth be told, there was no deal whatsoever with either Yaqub or the other Memons. No assurances were given to any of them at any stage. All claims of the Memons having been lured to return with promises of a lenient view being taken are bogus. I say this with all the sincerity at my command," he wrote in his book.